Patent Grant
9966055
The present disclosure relates generally to musical instruments and specifically to a pedal steel guitar instrument. More particularly, the disclosure relates to improvements in functional features and workings of the pedal steel guitar instrument, including improvements in the way the shifting of the pitches of individual strings is achieved; the way in which the instrument's pedals and knee levers, engaged by the player during the normal playing of the instrument, control the strings' pitch changes; and the way in which the parameters that govern the changes are programmed and used by the player.
The traditional pedal steel guitar was developed in about the middle of the 20th century. In the traditional instrument, the strings' pitches may be altered by machinery that physical stretches and loosens the strings. These pitch changes can be done while playing the instrument. The mechanical nature of the machinery used to alter the strings' pitches can be seen in
In the traditional instrument, each string has its own individual bridge 22 so that its tension can be altered individually (i.e., per string) as its bridge rolls towards or away from the nut. The rolling action of the bridge is accomplished by pulling on mechanical changers under each bridge. These changers are disposed inside, on the underside of the body, with access to the changers and supporting linkages being provided by a hole in the endplate 26. The series of mechanisms that impart motion of the foot pedals into movement of the bridge can be seen in
Attached across the base of the front legs is a pedal bar or rack 14 that supports a plurality of foot pedals 16. Three pedals are illustrated in
In the traditional instrument, a monophonic pickup 28 is mounted on the body, near the bridge 22. In the traditional instrument this pickup employs a magnetic solenoid that magnetically couples to the instrument's metal strings. When the strings vibrate, this string motion produces changes in magnetic flux, causing an electric current to flow in the solenoid, which is then conducted by a two-conductor cable to an analog amplifier (e.g., guitar amplifier). The pickup is positioned so that the strings pass over and in near proximity to the pickup, thus establishing good magnetic coupling between pickup and strings. In the traditional pedal steel instrument the pickup is monophonic. This means that vibratory movement of one or more strings are collectively captured as a single monophonic signal in which the sounds of the individual strings are merged into a single monaural output.
Because a traditional pedal steel guitar uses machinery to physically change the tension of strings to achieve musical pitch changes, it suffers from a number of problems and limitations which are inherent in the design of that machinery. The present disclosure solves a number of these problems and removes a number of these limitations, including but not limited to the following:
Weight: A traditional pedal steel guitar is heavy, due in great part to the necessary inclusion of the machinery.
String fatigue and breakage: In a traditional pedal steel guitar, the constant changes in string tension cause wear on the strings themselves, weakening them and causing their tone to degrade over time. Strings can break and it is usually necessary to replace strings often.
“Splits”: In a traditional pedal steel guitar, when a string can be altered by more than one pedal, and the pedals individually alter the string tension in opposite directions, the resultant pitch will often be slightly out of tune. For example, one pedal, when engaged alone, might raise a string's pitch a whole step while another pedal, when engaged alone, might lower the same string a half step. When both pedals are engaged simultaneously, the sum of the two changes should result in a half step raise of the string. However, it is often the case that the sum of the physical tension changes is not precise and the resulting pitch is not precisely the intended pitch. Compensation is necessary, which usually takes one of several forms: an adjustment of the bar held in the player's left hand while playing; the manipulation of how rods and changers are connected and adjusted (with the concomitant effort and time to make these adjustments, sometimes requiring the help of someone specializing in working on pedal steel guitars); or the use of “compensators” (added machinery, with concomitant added complexity and weight) to make up for the difference.
“Cabinet drop”: In a traditional pedal steel guitar, string tension changes associated with engaging of pedals can stress the body of the instrument enough to cause other strings, not intended to be altered by these pedals, to be temporarily slightly out of tune. Some conventional pedal steel guitars are outfitted with “compensators” to adjust for this problem.
Pedal travel and “feel”: The kinesthetic sensation and physical feedback that a traditional pedal steel guitar player senses and how far a pedal travels in order to fully engage must often be adjusted by physically altering where on a bellcrank and/or on a changer a pull rod is attached since different positions have different travel and leverage.
Half-pedaling: If a pedal/lever raises or lowers a string by a whole step, a player can engage the pedal/lever only part way and achieve a pitch change of a half-step. This requires experience and skill. In some cases, traditional pedal steel guitars are equipped with adjustable springs to help the player feel when the half-way point is near or has been reached. Without such an adjustment, getting a half-pedal to sound in tune is difficult. With an adjustment, the extra effort of tuning the adjustment is required.
The present disclosure addresses the aforementioned problems and limitations of the traditional pedal steel guitar, without altering the distinctive sound of the instrument, or the manner in which it is played. This is accomplished by providing a digitally pitch-shifted pedal steel guitar that implements a copedent through the use of controlled pitch-shifting by digital signal processing rather than through the use of a physical mechanism to change the tension of strings. The term copedent is a term of art used by pedal steel guitar players to describe how string tunings, foot pedals and knee levers are combined to effect different tunings of the instrument. Copedent information is often expressed in table form, showing what pitch is developed for each open string (unfretted or unstopped) for a given combination of pedal and knee lever engagements. Thus the digitally pitch-shifted pedal steel guitar of the present disclosure implements copedent operation by digital electronic means rather than by changing physical string tensions.
More specifically the “copedent” is the logical heart of a pedal steel guitar. A copedent is depicted as a table with rows representing strings and columns representing pedals and knee levers. The intersection of the rows and columns contain the pitch changes that particular pedals/levers may make to particular strings. A copedent is realized in a traditional pedal steel guitar in the physical realm by mechanical means through the machinery (i.e., rods and bell cranks and changers) and as these mechanical components are affected by engaging the pedals and knee levers, the tension and pitch of one or more strings will change continuously up to, or down to, the pitch shown in the copedent.
By contrast, the present disclosure realizes copedents using digital signal processing. Doing so allows copedents to be created, edited, saved, recalled and used in playing, through the use of electronic components and processors. Changes in pitch are achieved by real-time digital signal processing which is continuously controlled by data from the software (processor instructions), as explained in the present disclosure, as the processor takes data input from sensors measuring the travel ranges of each pedal/lever.
In addition to addressing the aforementioned problems with traditional pedal steel guitar instruments, the digitally pitch-shifted instrument eliminates a variety of shortcomings of the traditional instrument, and offers a number of unique advantages, including but not limited to the following:
Need to tune pedals: On a typical traditional pedal steel guitar, the strings of course are tuned while open. In addition, the pedals and knee levers need to be tuned as well; that is, the pitch which strings will reach when pedals that affect them are engaged need to be tuned as well. This usually involves using a wrench to turn a nut on the end of a pull rod such that the effective length of the pull rod is slightly changed. This in turn will cause a change in the tension ultimately reached when a pedal is fully engaged, which in turn changes the ultimate pitch reached.
Difficulty in changing copedents: If a traditional pedal steel guitar player wants simply to experiment with a new copedent, or even make a small adjustment to an existing copedent in the form of a single simple pedal change, time and effort are required to remove and reinstall parts of the machinery, make adjustments, and retune. Restringing the instrument with strings of different gauges might also be required.
Number of necks: Most traditional pedal steel guitars have one or two necks of ten or twelve strings each (though other numbers of strings per neck are possible), each with a range of string gauges appropriate for the strings' open-tuned pitches. Two necks afford a traditional pedal steel guitar player two different copedents with different sounds, often used for different styles of music. The history of the traditional pedal steel guitar and the styles of music traditionally played on it have steered the evolution of two main standard copedents, though others do exist. Many players also add a few personal changes to otherwise standard copedents.
Number of raises and lowers per string: A “raise” is the increase in tension, and raise in pitch, by one pedal of one string. A “lower” is the decrease in tension, and lowering in pitch, by one pedal of one string. Most traditional pedal steel guitars have a limit, due to their physical design, of the number of raises and lowers on any one string. For example, many traditional pedal steel guitars afford no more than three raises and two lowers.
Physical limit on range of intervals: There is a natural, physical limit on how much a string can be tightened without its breaking or loosened while still maintaining playability and tone. Most traditional pedal steel guitars do not raise or lower a string more than a minor third, or perhaps major third.
Playability identical to the traditional pedal steel guitar: The present disclosure's elimination of the machinery of the traditional pedal steel guitar, while keeping other parts and aspects of the traditional pedal steel guitar (namely, those with which the player comes into contact when playing; e.g., strings, pedals, knee levers), the manner in which a player interacts with the instrument remains unchanged and the player does not need to alter anything about their technique or acquire new skills.
Reduced weight: By eliminating the machinery of a traditional pedal steel guitar, the instrument can be made to be much lighter, facilitating transportation and set up.
Ease of maintainability: The elimination of the machinery, including the roller nut and moving changers (at the bridge end) of the traditional pedal steel guitar also eliminates nearly all of the mechanical maintenance work that a pedal steel guitar player does to keep the instrument in playable condition and eliminates most worries about tuning the instrument.
Effectively zero string fatigue and string breakage: By removing the need to stretch or loosen strings physically, string fatigue and breakage are essentially eliminated. Again, no machinery is needed, only a simple bridge and a simple nut are required on which to mount the strings, making building and maintenance of the physical parts of the instrument simpler and less expensive.
Programmable, storable, recallable copedents: By using electronic hardware and software along with pitch-shifting DSP to manipulate strings pitches, the player is, without physical effort, specialized knowledge or skill in the maintenance of the machinery of the instrument, free to create, change, store, and recall any number of copedents and be assured that they will be in tune without the effort of changing strings or retuning the pedals. With a reasonable number of physical pedals and knee levers (for example, five pedals and five knee levers, though more are possible) essentially all existing common copedents as well as an unlimited number of copedents never before possible are easily implemented. Furthermore, changing between stored copedents takes only moments using the user interface.
Virtual capo: Capos exist for guitars which allow a player to raise by half-steps the pitches sounded by the open-tuned strings by physically stopping the strings at a position between the nut and bridge of the instrument, effectively acting as a new nut. Capos do not exist for the traditional pedal steel guitar (such a capo would have to have a roller mechanism and would be extremely difficult to install and remove). The present disclosure affords the player the ability to virtually capo (through digital pitch shifting) the chosen tuning/copedent by half-steps, up in pitch or even down (something not even physically possible in a traditional pedal steel guitar or regular guitar).
Tuning adjustments: Since pedal/lever-affected pitches as well as open strings need to be tuned on a pedal steel guitar, when accompanying other instruments which may not be tuned to standard pitch, retuning a traditional pedal steel guitar to match them is tedious and time-consuming (requiring retuning strings and retuning pedals/levers). The present disclosure can digitally adjust the entire tuning of the instrument by any amount. For example, one can easily move the entire instrument's tuning and copedent up or down by any number of cents (1 cent=1/100 of a semitone).
Pedal “feel”: A traditional pedal steel guitar player senses the change in string tension while playing. The amount of pressure needed to engage a pedal or lever and the resistance felt are a function of the string tension itself and the different amounts of leverage at each point in the machinery related to that pedal/string change. The present disclosure allows for the simplification of this aspect of the adjustment and maintenance of a pedal steel guitar. For example, one embodiment of a pedal steel guitar incorporating the present disclosure would use a physically adjustable spring for each pedal/lever. A return spring would be needed in any case for each pedal/lever, but as the strings themselves never change in tension, by making such a spring adjustable, the player could customize pedal feel independently of the tension of the strings affected.
In-tune splits: In the present disclosure, the behavior and precision of splits are managed by software control of pitch-shifting DSP. Therefore, when engaging multiple pedals that affect the same string, it is software control which accurately sums the programmed individual changes, causing the string to reach its final pitch precisely.
Half-pedaling: With the present disclosure's use of software-based pitch-shifting, a half-pedal is achieved by separately saving, as part of a saved copedent, a pitch that falls within the pitch interval from virtual open string pitch to the pitch achieved by fully engaging a pedal. For example, if a pedal raises a string a major third, a half-step raise could be saved as a “half-pedal” position such that as the player approaches a particular physical point within the full travel range of a pedal/lever, the pitch of the output is “attracted” to a half-step above the open pitch of the string. As the pedal/lever travels past a threshold beyond that point, that “attractor,” the remaining interval of the pitch-shift continues to be applied (in this case, a minor third). In this sense, the term “half pedal” is a somewhat inaccurate term since the “half-pedal” pitch is not half of the interval corresponding to the full travel of the pedal. This could even be implemented on more than one string where the strings are affected by the same pedal.
A “multiple stop half-pedal” is also possible. The player may choose to have more than one intermediate position/pitch/attractor.
A “multidirectional half-pedal” is also possible to have a “half-pedal” that changes direction. For example, a pedal could begin to lower a string's pitch until it reaches an intermediate travel position, or “attractor.” As the pedal continues past that position, it could change direction and raise the string to some other pitch, identical to or different from its original virtual open pitch.
“Meta-splits”: The present disclosure allows for one or more particular pedals to be programmed in such a way that they alter the behavior of another pedal or pedals, as opposed to merely summing their own change(s) with the change(s) of another pedal or pedal, as in the case of splits.
Size of pitch intervals: As the pitch changes are no longer dependent upon the physical changing of string tension, there are no theoretical limits to the interval to which a string's pitch may be raised or lowered.
Most of these enhanced and unique behaviors are impossible on a traditional pedal steel guitar.
Therefore, according to one aspect of the present disclosure, the instrument includes a body, legs, a plurality of strings, a plurality of pedals and/or knee levers in the general structure and configuration of a traditional pedal steel guitar. A plurality of transducers to capture the vibration of each string individually is deployed on the instrument. A plurality of analog to digital converters (ADC) convert analog vibrations of the strings into digital signals that are then operated upon by a digital signal processor.
The digital signal processor is programmed to independently digitally pitch shift (e.g., by means of software-based DSP), in real time, the separate digital signal outputs of the ADCs. The digital signal processor receives messages sent by a main control program which encapsulate sensed data indicative of the travel of each pedal and/or knee lever. The signals, after processing are both summed and sent to a DAC (or sent to multiple DACs and then summed in the analog realm) for output as standard pedal steel guitar output and also kept separate for output as independent digital signals, one per string for further external processing if so desired.
A user interface is further provided through which the user or player can interact with the electronic aspects of the instrument.
Although the digitally pitch-shifted instrument handles copedency electronically, the instrument nevertheless has a familiar, traditional feel to the player. This is accomplished through springs attached to the pedals and knee levers to provide physical resistance and therefore kinesthetic feedback to the player of the instrument. These same springs also cause the pedals and knee levers to return to their original, at-rest position after being released by the player. As a result, the instrument feels like a traditional pedal steel guitar, even though the tunings are produced by an entirely different means. Thus while the disclosed instrument differs from a traditional pedal steel guitar instrument in a number of important respects, it remains playable in precisely the same way as a traditional pedal steel guitar.
Moreover, all features and advantages of the disclosed digitally pitch-shifted pedal steel guitar require no alteration to the way in which the instrument is played. Therefore, no changes in knowledge, skills, or techniques are required by a traditional pedal steel guitar player when moving to a pedal steel guitar incorporating the present disclosure. The player needs to invest no time or effort in learning new techniques required to play a new instrument.
Software (program instructions) running on a micro-processor or other processor for copedent control is capable of modifying, saving, recalling software-based copedents and of calculating, based on pedals/knee levers travel sensor output, control information to be sent to the DSP processor(s).
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Several drawings of an exemplary traditional pedal steel guitar are included as context for what improvements are made by the disclosed invention; e.g., in the disclosed embodiment(s) no conventional pull rods are needed, nor are bellcranks or cross rods or changers needed; multiple output channels may be summed or taken separately; software implementation of copedents affords instantly changeable tunings, in-tune “splits,” etc.
In the disclosed digitally pitch-shifted pedal steel guitar instrument, the pedals may transfer their travel to sensors housed in the body of the instrument by means of pedal rods, just as they do in the case of a traditional pedal steel guitar. Alternatively the pedals may be supported by attaching to the instrument legs or pedal bar/rack, or they may be freestanding and electrically coupled to the electronic circuitry by wire or wireless communication. The drawings here assume the first case.
Different kinds of pickups may be used as long as each string is given a separate audio channel. The drawings here assume magnetic pickups.
The next several figures show a series of mockups of a touchscreen which is used by the player to interact with the software in order to configure various musical aspects and capabilities of the instrument.
By outward appearance, the digitally pitch-shifted pedal steel guitar looks similar to a traditional instrument, however, there are numerous technical differences. Thus as seen in
However, unlike the traditional instrument, the foot pedals and knee levers are not mechanically coupled to cause physical stretching or loosening of the strings. Indeed, in the digitally pitch-shifted pedal steel guitar instrument the strings do not need to be physically stretched or loosened to change tunings. That is all done electronically and without the need to change string tension.
A touchscreen 102 is provided to allow the user to change settings within the instrument and thus change how the foot pedals and knee levers perform. The placement of the touchscreen 102 in
Also, the multi-element pickup 28a is a more sophisticated pickup that can obtain pitch information from each string individually. One embodiment of a suitable pickup 28 is shown in
The digitally pitch-shifted pedal steel guitar provides a group of external connections, shown in
Pedals and Levers Operate Electronically, Yet Retain Familiar Feel
Referring to
The manner of mounting the cross rod 58 to the roof of the instrument body 50 is shown in
Digital Signal Processing of Each Individual String
In the preferred embodiment of the digitally pitch-shifted pedal steel guitar, all strings are supported by a single bridge, as there is no need for independently moving bridges as in the case of a traditional instrument. As each string vibrates, its vibrations are captured by its associated pickup or transducer as one analog signal for each string. The analog signal for each string is transmitted through a cable connection to its associated ADC. Each separate channel of, now digital, audio signal will be acted upon by the pitch-shifting DSP processor downstream.
Referring to
Meanwhile, output data (f) from the Hall Effect sensors 70 on each of the pedals and knee levers are read by the Microcontroller (MCU) 94. The MCU 94 calculates pitch shift values and sends them via messages (e) to the DSP processors 92. The DSP processors alter the pitches of the appropriate signal channels. The separate digital signals are summed and sent as a single digital signal (c) to the digital to analog converter (DAC) 96). Though that is what is shown in
From there, it can be output through a standard ¼″ TS jack to an audio amplifier (not shown). In addition to the single summed output signal, the several digital signals are also sent separately (d) to a USB output port 98. The DSP processors can also send data (e.g., pitch tracking data, and pedal/knee lever travel data) (e) to the MCU for tuning and string calibration, and pedal knee lever sensor calibration.
The MCU communicates (h) with the touchscreen controller 100, which in turn communicates (g) with the touchscreen 102 to allow the user to interact with the main program running on the MCU. Saved copedent data is saved to and read from EEPROM 104.
Note: All components may be housed on the same circuit board or the system may be modularized with different components on different circuit boards connected by cables.
Also as discussed above, the output of the pitch shifting process 106 can be supplied in digital form (d) via a suitable interface, such as through a USB port 98. These digital domain signals can retain the data for each string as a separate digital channel, thus making it possible to process the data from each string separately and possibly in a different manner.
In
At the start of this endless loop, the WorkingStringArray (an array of length equal to the number of strings) is initialized, each position in the array is loaded with the sum of the following values for the corresponding string:
After initialization of the WorkingStringArray, the Pedal/Lever Loop is entered at steps 128 and 130. For each pedal/lever, the corresponding sensor is read at step 140. If the sensor's output is within a threshold of the last value read for that sensor (step 142), the loop moves on to the next pedal/lever (step 144), since the pedal/lever must not have moved significantly. Otherwise, if the difference between the output value and the last value is larger than the threshold (at step142), then the value is checked to ensure that it fall within the range of the maximum and minimum values stored for that pedal/lever's travel (if the value is within a threshold of the maximum, it is set to that maximum value; if it is within a threshold value of the minimum, it is set to that minimum). Then, the last value for that string is updated with the newly read value.
Embedded within the Pedal/Lever Loop is the String Loop (beginning with step 150), which is concerned with adjusting the values held in the WorkingStringArray. In the String Loop, for each string, if there is no change dictated by the copedent for that string and pedal/lever combination (step 154), the mapped Value variable is set to zero at step 156. If there is a change dictated by the copedent for that string and pedal/lever combination, then the mapped Value variable is set, at step 160, to a value mapped from the point in the pedal/lever's minimum to maximum travel range into a range from zero to the number of semitones up or down dictated by the copedent for that pedal/lever and string combination.
The value of the mapped Value variable is then added, at step 158, to the value originally set in the WorkingStringArray at the beginning of the endless loop. This effectively sets a value that combines those summed values with the momentary pitch change calculated from the pedal/lever's travel.
The program proceeds to the next string in the loop, checks whether any change is dictated by the copedent for that string and pedal/lever combination, then sets the mapped Value variable to either zero or a mapped value, and adds it to the WorkingStringArray for that string.
By the time all pedal/levers and strings are considered by the two loops, the WorkingStringArray will contain one value for each string. Each value represents the sum of all variables needed by the DSP to shift the each string's channel's pitch for that moment in time.
With all the strings' values updated at the end of one iteration of the Pedal/Lever Loop, the main control program proceeds to a new, different loop, at steps 132 and 134. For each position in the WorkingStringArray, that is, for each string, the value in the WorkingStringArray is encoded into a message at step 136 containing the number of the string/channel and the value in the array (in the preferred embodiment, the Open Sound Control protocol is used for encoding and decoding these messages). The message, sent via some standard communication protocol capable of addressing multiple peripherals (such as SPI), is sent to the DSP processor handling that particular channel. The DSP processor decodes the message and adjusts the current pitch of the particular channel addressed in the message, by the amount sent in the message.
Processing then returns to the main endless loop at step 126 where the WorkingStringArray is refreshed and the Pedal/Lever Loop is entered.
For a more complete understanding of how the digital pedal steel guitar may be implemented, computer code excerpts and a pseudocode description is provided at the end of the disclosure. Included with these code excerpts is a description of the variables, functions and code used by the main control loop.
Discussion of How Copedents Work
To understand how the digitally pitch-shifted pedal steel guitar instrument affects different tunings, an understanding of copedents will be helpful.
As described in
The conventional names for pedals are as follows. For a standard E9 copedent, shown in
In the cells at the intersections of strings (rows) and pedals/levers (columns), the number of half-steps that particular pedal/lever should raise or lower the pitch of that particular string and/or the actual pitch name achieved by engaging the pedal/lever.
If a cell is empty, the pedal or lever does not affect that string. If a pedal or lever does affect a string, there are two commonly used ways of denoting that fact in a copedent: either the note name of the altered pitch is written in the cell or the number of semitones up or down is written in the cell. Therefore, if a cell contains a note name, the string will move up or down to that note's pitch. Alternatively, if a cell contains a signed numeral or one or more plus signs or negative signs, for example, +2 or −1 or (++ or −), the string will move up or down that number of semitones. Sometimes, both are used, e.g., “++A.” Note that, in the particular copedent illustrated in
A copedent is realized in a traditional pedal steel guitar in the physical realm by mechanical means (i.e., rods and bellcranks and changers, aka “machinery”). As the machinery is engaged via pedals/levers, the tension and pitch of one or more strings affected by a pedal/lever will change. Each string will change continuously up to or down to the pitch shown in the cell of the copedent table where that string and pedal, or lever, intersect. Note that
By contrast, the digitally pitch-shifted pedal steel guitar realizes copedents in electronic hardware and software. As pedals/levers are engaged, the software receives data from sensors about the pedals' and knee levers' movements. It uses those data in conjunction with the software copedent currently in force to calculate values to be used to control real-time digital signal processing (DSP), and sends these values to the processors to accomplish that processing.
This transfer of copedents from the physical realm to the software realm further allows copedents to be created, edited, saved, and recalled, and allows copedents which are impossible to realize in the traditional pedal steel guitar. For example, in the traditional pedal steel guitar pitch change intervals are always limited by how far a string could be tightened before breaking or loosened before losing its tone. Another limit of the traditional pedal steel guitar is the number of strings that might be changed with one pedal or knee lever, since the resistance of strings or return springs is cumulative. And so, more generally, the present invention is a novel method of easily implementing and changing an essentially infinite number of copedents.
In the digitally pitch-shifted pedal steel guitar, the machinery of a traditional pedal steel guitar is replaced by a system of electronic components including sensors, audio ADC and DAC, DSP, and control processor (e.g., a micro-processor), along with software in both the DSP and control realms. It is this control realm of software (copedent-related user interface and control) that is the present invention.
User Interface of the Digitally Pitch-Shifted Pedal Steel Guitar
The processor(s) of the digitally pitch-shifted pedal steel guitar operate in accordance with a main control program, the details of which are discussed below. In the preferred embodiment, the main control program presents a user interface through which a user/player may enter data and adjust various aspects of the instrument and the main control program. If desired, the user interface can be displayed upon an LCD display panel mounted to the surface of the instrument. Alternatively, the user interface can be displayed upon a separate device, such as via an app running on a tablet display device (e.g., iPad) or smartphone. To give a flavor of the types of things the user can do via the user interface, the following examples are provided. It will be appreciated that a variety of features can be implemented on the digitally pitch-shifted pedal steel guitar, and the following examples are not intended to be exhaustive.
Manipulating Copedents
With regards to copedents, as described earlier, the user may enter data to create new copedents or make changes to existing copedents. That is, through the user interface, the user/player may recall, delete, edit, save, and use in playing, any number of virtual copedents. Therefore, through the user interface, the user is able to program the “virtual open string” pitches as well as to program the individual pedal and lever changes to each string's output pitch.
The way different pedals/levers interact when engaged simultaneously, e.g., “splits” and “meta-splits” as well as “half-pedals” (including “multiple stop half-pedals” and “multidirectional half-pedals” can be programmed as well through the user interface.
The user interface is also used to make other musical adjustments to the instrument such as:
In contrast, in the present disclosure, through the use of a menu, the user is able to switch between saved copedents quickly. Alternatively, “banks” may be used. Each bank displays multiple saved copedents and the user can switch through different banks (
Again, copedent changes in the present invention may be more complex than in the case of the traditional pedal steel guitar in that they may include pitch change intervals impossible to achieve through string tension changes, priority and additive splits, meta-splits, and multi-position and multidirectional half-pedals.
In this embodiment of the present invention, the user interface is described in some detail here:
Choosing to tune the physical open strings, when the user selects the corresponding item from the menu, the software is put in a mode which waits for input from the separate transducers. As the strings are plucked, the actual pitches of the strings sounded are tracked and displayed on the UI (
Another aspect of the UI is the option to calibrate open string pitches to standard tuning. After the user tunes the physical strings, this mode can be used to make automatic adjustments to the virtual open string pitches so that they each remain precisely at the copedent's intended pitch even if the physical string goes slightly out of tune over time or while playing. In this mode, the software precisely compares the actual physical string pitch with the pitch to which the user tuned the physical string. If the string has loosened slightly and is, for example 4 cents flat from the intended physical open string pitch, then enough pitch correction will be added to the workings of the main program. If another string is slightly sharp, its channel can be compensated independently and differently during the playing of the instrument as the main program calculates all DSP control. That is to say, these values will be used as a starting point for all pitch-shifting calculations during the continuous processing to control the DSP pitch-shifting during the playing of the instrument.
Sensor Calibration
Should sensors be employed on pedals and knee levers that from time to time require recalibration of the beginning and ending points of their range of motion, the user, choosing to calibrate pedal/lever travel, selects the corresponding item from the menu. The software is thereby put in a mode which waits for input from the engaging of pedals and knee levers (
Setting Up a Capo
Choosing to set a capo value, the user selects the corresponding item from the menu. The software is thereby put in a mode which waits for input from the user in the form of a positive or negative integer value, which will be used as the number of semitones up or down from the virtual open string pitches (
Making Fine Tuning Adjustments
Choosing to make a fine tuning adjustment (for example, in order to be in tune while playing with others who are not necessarily tuned to standard A440), the user selects the corresponding item from the menu. The software is thereby put in a mode which waits for input from the user in the form of some pitch adjustment; e.g., cents up or down (
Copedents
Choosing to recall an existing, stored copedent and use it to play, the user can choose from a menu or scroll list of copedents stored in non-volatile memory. Then, choosing to “Play” (
Choosing to create a new copedent, the user can choose an existing, stored copedent that is similar to the copedent desired from a menu or scroll list of copedents stored in non-volatile memory. The user can then edit the values of this copedent and save it as a new copedent (
To edit a virtual open string pitch, the user touches the open string value in the left column. This presents a slider, much like the one used for capo editing, which can be used to raise or lower the pitch of the virtual open string.
To edit a pedal/lever change, the user touches a “cell” (the intersection between a string's row and pedal or lever's column). This presents a slider, much like the one used for capo editing, which can be used to raise or lower the pitch of that particular string to be achieved when engaging the pedal or lever.
Once all changes are made, the user can touch the “Save” button so that the newly created copedent can be stored in non-volatile memory for later recall and use. Alternatively, the user can touch the “Cancel” button to discard any changes made.
Saving Copedents for Later Recall
Once copedents are saved, they may be grouped in a “bank” of several copedents to afford quick changes which might be used during a performance. While playing, a screen like that seen in
Control Program of the Digitally Pitch-Shifted Pedal Steel Guitar
As seen in
In “string calibration” or “tuning” mode, the digital audio signals (k) are received by the pitch-tracking function 110. Pitch-tracking data (j) are sent to the micro-controller (MCU) (10) via some kind of serial message (e.g., MIDI, Open Sound Control, etc.). These data are ultimately displayed to the user by being sent as flat, sharp, or in-tune note information (m) to the touchscreen controller 100 which is in charge of communicating to the touchscreen 102 via (g). The user can tune the physical open strings until the touchscreen indicates that the pitches coming into the pitch-tracking function are in tune.
In “pedal calibration” mode, as the user engages the pedals and levers, the minimum and maximum values of the sensors (70), corresponding to the at-rest position and the fully engaged position of the pedals and levers, are sent (f) to the MCU. The MCU saves these position data in memory, also sending them (o) via some serial protocol (e.g., SPI, I2C, I2S, etc.) to EEPROM (104) for longer-term storage, so that upon the next restart, the previous calibration values can be read (p) and reused.
In “edit” mode, the user interacts with the touchscreen (102). User touch data (q) is sent to the touchscreen controller (100) which translates as necessary and sends that data (n) to the MCU. The MCU will record the user's changes and send the data (o) to EEPROM for longer-term storage. This data includes copedent values, virtual capo values, and virtual tuning adjustments.
In “copedent” recall mode, the user again interacts with the touchscreen by requesting to recall a copedent from EEPROM. The request through (q) and (n) is managed by the MCU and the data is loaded from EEPROM via (p) into the MCU's memory.
In “play” mode, the transducers (28a) send their analog signals (a) (of strings played open or fretted/barred) to the ADCs (90). The digital output signals (k) are received by the DSP processors' pitch-tracking function (110). The DSP processors' pitch-shifting function (106) receives the pitch tracking data (I) along with the actual digital audio signals (b) themselves.
As the player engages the pedals and levers, the MCU, based on the copedent currently in effect, and on incoming pedal and lever sensor data (f), calculates the amount of pitch-shifting necessary for each channel. The results of those calculations are sent along with their corresponding channel, encapsulated in messages (e.g., MIDI, Open Sound Control, etc.) via (r) to the pitch-shifting function (106) in the DSP processor. The pitch-shifting function, in real-time, alters the digital audio signals which are then sent:
Note: All components may be housed on the same circuit board or the system may be modularized with different components on different circuit boards connected by cables.
Terms Used in This Document
As used herein,
This pseudocode assumes a touchscreen user interface and a micro-controller with two functions:
This pseudocode does not go into detail on other aspects of the program having to do with calibration and editing copedents and interfacing with other external devices and data. Rather it concentrates on just that data acquisition, computation, and messaging which is the present disclosure, the realization in software of a pedal steel guitar copedent for use in a digitally pitch-shifted pedal steel guitar.
The code has two main modes: UI (in which the user can interface with the touchscreen and through it, the system) and PLAY (in which the user can play the instrument with all values in effect).
The main loop checks the mode. If it is PLAY, the controller takes input and computes pitch-shifting values and sends messages to the processors. If the mode is UI, the code controls the touchscreen, sending values to and receiving values from the user, reading and writing values to EEPROM, etc.
The code assumes that the physical open strings have already been tuned by the user to certain prescribed pitches.
Note: Values for pitch adjustments are presented to the user in the user interface as either multiples of semitones or as cents, depending on what musicians generally expect (e.g., as semitones when thinking about non-microtonal open string pitches, capo values, and pedal/lever changes and as cents when “tweaking” the tuning of the instrument). When used in the actual code for calculations, all values are converted to either one or the other.
Other modes are possible. For example:
Note: values for those variables listed here may be set at different locations in the code, but their scope is global)
Pseudocode of Main Copedent and Control
Copedent Realizations
A typical E9 copedent is shown in the center of the figure, labelled “Conceptual Copedent.”
Above the copedent table, the figure shows how, in the case of the traditional pedal steel guitar, that copedent is realized in the physical realm by means of physical machinery; i.e., rods, bellcranks, changers, etc. In the traditional pedal steel guitar, the actual pitch changes are realized by using the physical machinery to physically stretch and loosen strings.
Below the copedent table, the figure shows how, in the case of the present disclosure, the copedent is realized by means of software and the pitch changes are realized by signal processing which is controlled by the copedent software.
b. Legs
In the preferred embodiment, housed in the right end plate (a) of the instrument is a standard barrel connector (23), e.g., 9.5 mm length, is used to accept DC power, e.g., from a standard wall adapter. This is used to power the active pickups and all electronics: the MCU, the sensors, the processors, and the ADCs and DAC, etc.
Also housed in the endplate is a standard ¼″ jack (25) to be used for the summed analog audio output for amplification or recording.
Also housed in the endplate is a Type-B USB jack (27) to output separate digital audio channels (one for each string, after processing) for any use, e.g., post-processing or recording.
The USB out can also carry other data sent by the MCU. For example, pedal and knee lever position data, current copedent data, physical open string pitch data, and virtual open string pitch data may be sent to a personal computer or other external device running software. One example of such software is a real-time auto-tablature program. In this case, after starting the program on the external device and software handshaking occurs between the that program and the MCU, as the player plays the instrument, this data can be used to determine the nearest fret at which strings are barred/fretted and which pedals and knee leers are engaged. This data can be used to create tablature for the pedal steel guitar.
The Micro USB jack (29) can be used to upgrade firmware on the MCU and DSP processor(s). It can also be used by an external program to download and upload saved copedents, e.g., for use in sharing between musicians.
A further embodiment of the present invention may use only one DSP processor to pitch shift multiple channels received from the ADCs.
A further embodiment of the present invention would have any number of strings and associated transducers, ADC and DAC channels, associated channels of pitch-shifting DSP, and any number of pedals and knee levers.
A further embodiment of the present invention would have sensors attached directly to the pedals, which are in turn attached to the pedal bar/rack such that pedal rods would not be necessary. The sensors' electrical connections could be run from the pedal bar up to the circuit boards under the body of the instrument.
A further embodiment of the present invention would have sensors attached to the pedals directly with the pedals being free-standing.
A further embodiment of the present invention would use piezo-electric pickups as the transducers.
A further embodiment of the present invention would use optical pickups as the transducers.
A further embodiment of the present invention would use potentiometers as sensors for pedal travel, with each potentiometer's shaft coupled to a pedal or lever's cross rod, either directly or indirectly through a U-joint. As a pedal or knee lever is engaged and a cross rod turns, it would move the shaft of a rotary potentiometer and a variable voltage could be read from the potentiometer. The potentiometer would continuously send its variable output through the output wire to the micro-controller (MCU). A spring would have enough tension to give kinesthetic feedback in the form of resistance to the player and to return the pedal and potentiometer to their at rest positions.
A further embodiment of the present invention would use potentiometers as sensors for pedal travel, with each potentiometer's shaft coupled indirectly to a cross rod through a rack and pinion assembly. As a pedal or knee lever is engaged, the pedal rod would move downward, transferring its energy to a rack and pinion assembly which in turn rotates the potentiometer, with no deflection of its shaft. The potentiometer continuously would send its variable output through the output wire to the micro-controller (MCU). A spring would have enough tension to give kinesthetic feedback in the form of resistance to the player and to return the pedal and potentiometer to their at rest positions.
A further embodiment of the present invention would use potentiometers as sensors for pedal travel, with each potentiometer's shaft coupled indirectly to a cross rod through a pulley system. As a pedal or knee lever is engaged and a cross rod turns, it would move the shaft of a rotary potentiometer through strings or cords connection the cross rod shaft and the potentiometer's shaft, and a variable voltage could be read from the potentiometer. The potentiometer would continuously send its variable output through the output wire to the micro-controller (MCU). A spring would have enough tension to give kinesthetic feedback in the form of resistance to the player and to return the pedal and potentiometer to their at rest positions.
A further embodiment of the present invention would use a combination of infrared (IR) light emitters and IR phototransistor as sensors for pedal travel. As a pedal or knee lever is engaged, a vane attached to the cross rod would interrupt the IR beam from the emitter to a greater or lesser degree. The collector's output variable voltage could be read.
Another embodiment of the present invention would employ a slide potentiometer connected to each pedal, pedal rod, cross rod or other object connected in some way to each pedal. As the pedal moved, the movable portion of the slide potentiometer would move, and its output variable voltage could be read.
Another embodiment of the present invention would have knee levers that are adjustable in the left/right direction for the comfort of the musician. A track could hold assemblies, each comprising a knee lever and its associated sensor. Some method (e.g., a thumbscrew) would release the assembly so that it could slide along a track from left to right and be re-secured in a new position.
Another embodiment of the present invention would have knee levers that are adjustable in the front / back direction for the comfort of the musician. Each knee lever could be released, slid forward or backward, away from or closer to, the musician and then re-secured.
This application claims the benefit of U.S. Provisional Application No. 62/376146, filed on Aug. 17, 2016. The entire disclosure of the above application is incorporated herein by reference.
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| Number | Date | Country | |
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| 20180053494 A1 | Feb 2018 | US |
| Number | Date | Country | |
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| 62376146 | Aug 2016 | US |
