Patent Grant
6995311
Not Applicable.
Not Applicable.
1. Field of the Invention
This invention relates to electrified stringed musical instruments such as electric guitars, electric basses, electric pedal steel guitars, and electric violins.
2. Background of the Invention
A fundamental fact of all stringed instruments is that the strings need to be tuned to some reference pitch to produce coherent and pleasing music. For example, the accepted standard reference pitch of a 6-string guitar specifies tuning the strings to correspond with the notes E, A, D, G, B, and E corresponding to the frequencies 82.41 Hz, 110 Hz, 146.83 Hz, 196.00 Hz, 246.94 Hz, 329.63 Hz respectively. To avoid ambiguity in identifying the-strings of a guitar used in the discussion to follow, a dual nomenclature will be used of the form E(6), A(5), D(4), G(3), B(2), and E(1), where the E(6) string is the lowest pitched string, and E(1) is the highest pitched string.
Pitch drift is a problem that plagues all stringed instruments. There are many variables that affect the instrument's ability to maintain pitch over time. The unintended consequence is that the strings drift out of a state of tune. Key factors that conspire and contribute to pitch drift include variations in temperature and humidity, the materials, design, and assembly techniques used in the instrument's construction, the mechanical containment and tuning system employed, the string quality and age, and the musician's playing technique. For hundreds of years, tuning the instrument has always been accepted as routine maintenance.
Instrument builders and manufacturers continue to be challenged to create instruments that can reliably maintain their pitch. There is a tradeoff of manufacturing costs versus pitch stability. At one extreme, exotic materials and careful construction can be employed. For example, an instrument made of carbon fiber materials, precision mechanical tuners, and very high quality strings may have very good pitch stability when compared to lesser instruments. However, the price such an instrument would command would place it out of reach of most musicians. Unfortunately, it would still suffer pitch drift which can be reduced, but not eliminated. Mechanical tuning systems just cannot be made to maintain pitch over time without human interaction and correction. At the other extreme, it's a given that less expensive instruments drift more easily and require more frequent tuning adjustments.
In addition to pitch drift, another unintentional pitch problem occurs simply because some musicians are less adept than others at tuning their instrument. This is especially true if they rely on their ears alone for the tuning procedure rather than using an electronic tuning aid. Patience plays a factor. More time and effort expended on the tuning procedure usually produces better results.
Temperament is a specification for the note pitches an instrument should produce. Intonation is a measure of how well the instrument actually produces them. The instrument maker designs and fabricates the instrument to accurately produce pleasing note intervals of the chosen temperament, hoping that his efforts produce an instrument with good intonation. Attention to detail in the design phase, and good control of manufacturing tolerances typically produces an instrument capable of accurate intonation. A poorly designed and manufactured instrument may not be capable of accurate intonation due to sloppy workmanship.
Guitars and basses are designed to produce notes of the Equal Tempered chromatic scale. The nut 200 (
The basic design of most fretted instruments makes slight compromises in intonation for simplicity of design. Guitars and basses use the “Rule of 18” to position the nut, frets and bridge saddles in appropriate relationships to produce reasonable Equal Temperament. This technique is not perfect. To quote from U.S. Pat. No. 5,404,783 Feiten, et al. (1995): “Unfortunately, this system is inherently deficient in that it does not result in perfect intonation. As one author stated: “Indeed, you can drive yourself batty trying to make the intonation perfect at every single fret. It'll simply never happen. Why? Remember what we said about the Rule of 18 and the fudging that goes on to make fret replacement come out right? That's why. Frets, by definition, are a bit of compromise, Roger Sadowsky observes. Even assuming you have your instrument professionally intonated and as perfect as it can be, your first three frets will always be a little sharp. The middle register—the 4th through the 10th frets—tends to be a little flat. The octave area tends to be accurate and the upper register tends to be either flat or sharp; your ear really can't tell the difference. That's normal for a perfectly intonated guitar.” (See The Whole Guitar Book, “The Big Setup,” Alan di Perna, p.17, Musician 1990.”
Intonation compensation is performed by precisely moving the bridge saddle to adjust the physical length of the vibrating portion of the string. This fine adjustment is performed as a normal setup procedure when an instrument is new. Readjustment is required over time due to many of the same environmental factors that cause pitch drift. Readjustment is also required when strings are replaced on the instrument and when other mechanical adjustments, such as a change of string height relative to the frets and fret board, occur.
Thus, common stringed instruments are a compromise between the relationships of the mechanical elements (nut, frets, and bridge saddles) plus fine mechanical adjustment to attain intonation accuracy for the specified pitch temperament.
To summarize the previous discussion on intonation and temperament, we will distinguish the three key concepts outlined above, as they will be addressed separately by the present invention:
1. Choice of temperament: There are multiple temperaments that can be used with stringed instruments. The most common are Equal Temperament, Just Temperament, and Well Temperament. Guitars, banjos, and basses commonly use Equal Temperament. Pianos commonly use Well Temperament. Just Temperament is less commonly used. There are times when the musician may want to manually alter the instrument to change pitch temperament.
2. Inherent limitations of intonation accuracy: A given instrument, even when perfectly adjusted for intonation, may still deviate from its target temperament because the instrument design was somewhat compromised to begin with. The variability of manufacturing tolerances also contributes to this problem.
3. Intonation adjustment: A given instrument may require readjustment for intonation within the temperament specification the instrument was designed for. Readjustment is necessary due to numerous environmental and mechanical factors. Intonation adjustment is considered a normal maintenance procedure.
Altered tunings are intentional pitch changes employed to perform certain musical pieces, or styles. Altered tunings may also be a preference of the musician based on musical technique and/or playing comfort. For instance, “dropped-D” tuning is commonly used with guitar, when the E(6) string is lowered two semitones to D. Another common guitar tuning is “open G” where the strings E(6) through E(1) are retuned to D-G-D-G-B-D respectively. A performing guitarist who uses altered tunings will typically employ multiple guitars, each tuned to an altered tuning pattern to avoid the inconvenience of retuning a single instrument during a performance.
Unfortunately, using an altered tuning can radically alter the string tension. On instruments with necks (guitars, basses, banjos, etc.) this changes the neck curvature and the relief of the strings to the fret board and frets, also referred to as the “action”. This can make the instrument more difficult to play, and can increase intonation error. To avoid this, instruments are typically adjusted appropriately for their altered tuning and kept that way. This is another reason many musicians employ multiple instruments in a performance, each setup for a different altered tuning.
A capo is a mechanical pitch altering device typically used on a guitar or banjo to temporarily raise the open unfretted position of play further up the fret board. A capo is shown as 860(
A capo can produce a couple of unintentional side effects. A capo may force the instrument out of tune, as the tension on the strings may be affected depending on:
A capo used on an instrument that has an intonation problem tends to amplify the problem because intonation error increases the further up the neck one plays. Thus, a capo can be a blessing and a curse for the musician.
Other types of mechanical pitch altering devices include bridge tremolo/vibrato units and “B-benders” for rapid pitch bend effects. Hipshot bass detuners and similar pitch altering devices are used to temporarily pitch alter one or more strings. These devices are unreliable in restoring the instrument to a state of tune after use. Tremolo/vibrato units are especially problematic in this regard. The tremolo/vibrato unit shown in 870(
Another deliberate pitch alteration occurs when a musician tunes the instrument to a higher or lower pitch to reduce or increase the string tension. Many guitarists flatten or lower the pitch of their guitars a semitone or more to reduce the string tension slightly to improve comfort and playability. Some believe it increases volume as well. A common detuning for guitar is a half-step or semitone detuning which changes string pitch to Eb, Ab, Db, Gb, Bb, and Eb.
Numerous patents address tuning improvements to conventional guitars and related stringed instruments in the mechanical domain using bearings, improved bridge designs, improved tremolo/vibrato mechanisms and so on. However, the patents listed below do not embody the novelty, scope or the key concepts of the present invention:
Patents describing automatic tuning systems, as listed below, use electromechanical devices incorporating motors and gears or other electromechanical means to maintain pitch. A processing unit senses the string pitch in a closed-feedback system and adjusts the tension on the string using an electromechanical actuator of some type.
Electromechanical tuning systems suffer from several major drawbacks:
Several commercial products are available that implement automatic mechanical tuning of the types described by this body of work, but due to high costs, complexity, and demanding power requirements, they have not attained mass market status and instead serve a niche for certain discriminating musicians.
In U.S. Pat. No. 5,973,252 Hildebrand (1999) describes an improved method for pitch correcting a single audio signal generated from musical instruments or from the human voice using a microphone. However, the scope of Hildebrand does not address pitch altering a stringed instrument with a plurality of strings as his invention does not process a plurality of audio signals in parallel. This would be required to alter pitch for multiple strings. It does not address intonation compensation in the context of a stringed instrument. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate tunings and temperaments. The Hildebrand invention also does not include in its scope the ability to be integrated into and become part of the instrument itself with the many advantages that may result. This patent does not embody the novelty, scope or the key concepts of the present invention.
A body of work exists that addresses methods of improving intonation and applying temperament adjustments. In U.S. Pat. No. 6,426,454 Gregory (2002) describes a mechanical redesign of guitars, basses, cellos, etc. to use the “Penta” tuning system where the instrument's strings are tuned in intervals of fifths rather than intervals of fourths as in conventional guitars, basses and cellos. While interesting, this invention and the instruments designed using the Penta tuning system are unconventional and would require a musician to learn a completely new instrument with the Penta tuning and have him play with other musicians using Penta instruments and music. This is a rather draconian principle and impractical when implemented in the real world.
In U.S. Pat. No. 5,501,130 Gannon, et al. (1996) and U.S. Pat. No. 5,442,129 Mohrlok, et al. (1995) describe methods to apply “Just” temperament pitch analysis to a keyboard instrument performance. This body of work does not address issues of handling stringed instruments with a plurality of strings. Nor does it address stringed instrument pitch alteration for pitch drift, intonation compensation, pitch shifting, pitch bending, and alternate tunings.
In U.S. Pat. No. 5,404,783 (1995), U.S. Pat. No. 5,600,079 (1997), U.S. Pat. No. 5,728,956 (1998), U.S. Pat. No. 5,814,745 (1998), U.S. Pat. No. 5,955,689 (1999), U.S. Pat. No. 6,143,966 (2000), and U.S. Pat. No. 6,359,202 (2002) Feiten, et al. describe improvements to fret, nut, and bridge dimensional relationships and adjustments to the “Rule of 18” that is typically used in designing fretted guitars and basses. The result is series of temperament profiles to slightly alter the tuning of guitars and basses to make more pleasing notes. However, Feiten's invention requires alterations to a conventional guitar by adjusting the placement of the nut to a minor degree from the convention of the “Rule of 18” plus requiring subtle pitch changes to alter the temperament. How well manufacturers and musicians will accept this change has not yet been proven. However, it is unlikely that this invention will cause abandonment of instrument design parameters used for hundreds of years of guitar building.
In U.S. Pat. No. 6,359,202 (2002) Feiten describes the “Feiten Tuning Tables” which defines different sets of correction values to correct intonation for acoustic guitars, nylon stringed guitars, and steel-stringed acoustic guitars, and basses. As will become evident later, a clever engineer can apply the “Feiten Tuning Tables” to an application of the present invention.
However, the Feiten and Gannon patents discussed above do not embody the novelty, scope or the key concepts of the present invention.
A body of work encompasses pitch correction in the context of an automated music performance applicable to karaoke machines, keyboard instruments, MIDI sequencers, and “Band in a Box” computer accompaniment software. These inventions do not address the pitch problems inherent in stringed musical instruments. These inventions do not embody the novelty, scope or key concepts of the present invention:
A body of work encompasses pitch correction in the context of synthesized tone generation. These inventions do not address the pitch problems inherent in stringed musical instruments. These inventions do not embody the novelty, scope or key concepts of the present invention:
A body of work encompasses pitch detection in the context of tuning devices and tuning aids for stringed instruments. In U.S. Pat. No. 4,196,652 Raskin (1980) describes an embodiment where his tuner device contains an electronic circuit to control a stepper motor to automatically tune a stringed instrument. This embodiment would fall into the category of “electromechanical tuning devices” upon which the present invention improves upon and exceeds in scope. The following tuning device inventions do not embody the novelty, scope or key concepts of the present invention:
A commercial guitar synthesizer product family, which includes the models VG-8 and VG-88 from Roland Corporation of Japan, has a pitch correction and pitch shifting function built in. However there are several crucial limitations to these products when applied to the general problem of pitch management and control:
Japanese patent number 2745215 publication number 09-006351 “ELECTRONIC STRINGED MUSICAL INSTRUMENT”, SHINSUKE, Roland Corp. 10-0101997, patent date Oct. 1, 1997, discusses how to pitch shift two sound sources, a synthesizer and a guitar, so that they match. This patent is specific to guitars and does not address the general category of all electric stringed instruments. In this patent, pitch shifting is performed by discrete “pitch shifter” logic, and not with a more economical and flexible solution using a general purpose processor and digital signal processing techniques. The presence of a footpedal control in drawings 2 and 6 of the patent indicates that this system is an accessory device that rests on the floor and thus is an inherently costly solution. While it addresses pitch shifting, it does not describe any ability to perform pitch shifting per string to create hybrid instruments, or to create pitch regions over the fret board. It does not address pitch bending to replace mechanical pitch bending devices on the instrument. It does not address pitch correction, nor does it address intonation compensation. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate temperaments. This patent does not embody the novelty, scope or the key concepts of the present invention.
A Japanese patent application pending review is application number 2000-220106 publication number 2002-041047 “PITCH SHIFT DEVICE”, GOUSUKE, Roland Corp dated Aug. 2, 2002. The described application is specific to a guitar, does not address the broad category of electric stringed instruments. It does describe pitch shifting for altered guitar tunings. It does describe pitch shifting to emulate guitar capo use. It does not address the ability to pitch shift individual strings to create hybrid instruments. It does not address the ability to create pitch regions on the fret board. It is an external device resting on the floor per drawing 4 of the application, intended to be foot operated. This is an inherently costly solution. It does not address pitch bending to replace mechanical pitch bending devices on the instrument. It does not address pitch correction. It does not address intonation compensation. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate temperaments. This patent application does not embody the novelty, scope or the key concepts of the present invention.
The present invention comprises an electronic data processing system that is integrated with an electric stringed musical instrument. The system automatically and continuously detects and corrects unintentional pitch drift, and applies intentional pitch alterations without reliance on manual or electromechanical changes to string tension. The system monitors each string separately and applies a pitch-alteration to the instrument's electronic signals using digital signal processing methods based on pitch parameters stored in a memory table. The result is a pitch altered signal output from the instrument.
There are many advantages to using the Pitch Processing System in an electric stringed instrument:
1. Stringed instruments can be made self-tuning without resorting to electromechanical tuning actuators. The instrument will always sound in tune regardless of string tension. Pitch drift is eliminated. Sloppy tuning by the musician can be automatically corrected. This greatly enhances the ease-of-use when applied to conventional instruments, and especially helps novice or impatient musicians.
2. The Pitch Processing System is inherently more reliable, consumes less power, and is less costly to manufacture and maintain than instruments using electromechanical tuning systems.
3. Altered tunings and temperaments can be preprogrammed into the Pitch Processing System and applied to the performance. With the press of a button, alternative instruments tunings and temperaments can be applied instantaneously by the musician. For example, by shifting the pitch of a guitar's strings down by a fourth interval, the guitar now produces the pitch range of a baritone guitar. Thus, the Pitch Processing System allows a single instrument to quickly “morph” into a different type of instrument. Changing a guitar to use Well Temperament rather than Equal temperament is as easy as pressing a button.
4. The Pitch Processing System allows guitars, basses, banjos and any other stringed instrument using a fret board, to have multiple independent pitch regions allocated to the fret board. This provides unique hybrid instrument variations. Refer to the guitar illustrated in
5. The Pitch Processing System allows the strings to be individually pitch shifted such that the strings can be configured to produce additional hybrid instrument variations. For example, one variation might include a bass/guitar hybrid combination. In this example, the lower two strings E(6) and A(5) can be pitch shifted down a whole octave, equivalent to the pitch range of the E and A strings of an electric bass. This way, a guitarist can play a bass accompaniment on the lower two strings while playing the upper 4 strings with conventional guitar tuning. Many different permutations of this concept are possible.
6. Performing guitarists and bassists frequently employ multiple instruments each tuned differently with an altered tuning. The ability of the Pitch Processing System to apply multiple instantaneous pitch changes to a single instrument removes the need to purchase and maintain multiple instruments.
7. When applied to guitars and banjos, pitch shifting using the Pitch Processing System eliminates the need to use a capo. The Pitch Processing System allows electronically altered open tunings, providing a “virtual capo” without the pitch irregularities and inconvenience of a capo.
8. Pitch bending accessories such as bridge tremolo/vibrato units, “B-benders”, and detuner accessories can be eliminated as these functions can be performed electronically by the Pitch Processing System. The Pitch Processing System can be employed to apply electronic real time pitch shifting, thereby replacing the functions of mechanical pitch bending devices. The dynamic pitch bending effects of a tremolo/vibrato or other pitch bend device can be preserved while eliminating this mechanical source of unintentional pitch drift. An electronic control such as a pitch wheel, joystick, pressure sensor, or similar touch input device can send real time pitch bend information to the Pitch Processing System. This has the added benefit of lowering the cost of the instrument by eliminating the cost of the mechanical pitch bend accessory unit.
9. Produced in volume, a standard, high-volume Pitch Processing System implementation could be used on a multitude of different types of instruments. In high volume, it is expected that this system would add approximately $20 to $50 to the cost of the instrument. However, considering that it fulfills the same purposes of equipment that many musicians purchase separately (electronic tuner, outboard effects devices, extra guitars for alternate tunings, etc.) it could potentially lower a musician's overall equipment cost by several hundred to several thousand dollars.
10. Intonation errors can be automatically corrected by the Pitch Processing System. This reduces or eliminates the mechanical maintenance required to correct intonation problems. The result is a lower cost of ownership and improved customer satisfaction.
11. Strings can be selected with more degrees of freedom. For example, the string gauges typically used on an electric guitar are specified to maintain a target tension range, with the goal of producing the correct musical pitch while keeping the forces on the instrument within reasonable limits. With the Pitch Processing System, since the actual pitch of the strings does not matter, strings can be chosen with dimensions larger or smaller based on the musician's preference or instrument builder's specification to improve comfort, playability, or manufacturability. Lowered string tension also has the beneficial effect of extending the useful life of the strings and reducing string breakage.
12. It is entirely conceivable and practical to apply the Pitch Processing System to new instrument designs in a creative and unconventional way. Designers and engineers can take full advantage of the Pitch Processing System's ability to manage the instrument's pitch profile, as well as provide additional processing functions. Unique instrument designs using unconventional materials and fabrication techniques can be used. For example, it would be possible to construct an instrument out of very lightweight materials, such as balsa wood, cardboard, or inexpensive plastics.
13. When applied to traditionally styled conventional electric stringed instruments such as electric guitars and basses, the Pitch Processing System can be retrofitted into the instrument with minimal impact on the instrument's appearance, aesthetics, weight, balance, or sonic character.
14. Many guitarists prefer certain traditional instruments for their characteristic sound from their conventional magnetic pickups shown as 850 and 852(
15. The Pitch Processing System, being an entirely electronic pitch altering solution, can be powered by inexpensive batteries and not suffer the high power liability inherent in electromechanical tuning systems. Also, it is possible to incorporate additional power conservation and power management techniques using power managed semiconductor devices and power management software to further extend battery life.
16. With the potential to reduce or eliminate much of the external equipment a musician may need, the Pitch Processing System will increase overall equipment reliability by minimizing the number of external devices, cable interconnects, and power supplies used by the musician.
17. The Pitch Processing System can provide data processing functions enabling the instrument to transmit and receive non-note information. For example, the instrument can be connected to an external computer to receive memory table updates with pitch information constructed on the external computer. Another example would be to enable the musician to control an external computer from the controls on the instrument by transmitting control information.
18. When applied to electric-acoustic instruments such as electrified acoustic guitars, the Pitch Processing System can be employed to deliver the electronically produced sound for the benefit of recording equipment and sound reinforcement systems which has been very accurately pitch altered.
There are also second-order advantages of using the Pitch Processing System in an electric stringed instrument:
1. The Pitch Processing System is scalable for future enhancements. This will allow more audio processing features and functions to be added in the future via software upgrades and hardware upgrades as they become available. As processor performance improves, new capabilities can be added. Costs of the electronic modules can be lowered by reducing component count as higher integration devices become available. Power consumption will be reduced as semiconductor technologies evolve with lower operating voltages, and smaller device geometries.
2. Sound effects processing (echo, flanging, distortion, tone synthesis, etc.) that is done today using electronic devices external to the instrument can be incorporated into the instrument using the Pitch Processing System.
3. The Pitch Processing System provides a conventional electronic tuner function, with the advantage of being built into the instrument for convenience.
4. The Pitch Processing System can provide a headphone amplifier output function for private listening with headphones.
5. The Pitch Processing System can provide a built-in metronome function for time keeping while listening through headphones for private listening.
Further objects and advantages of the present invention will become apparent from a consideration of the drawings and ensuing description.
a shows a program flow chart of a software function described in an additional embodiment.
This invention is an enhancement to common electric stringed instruments, such as electric guitars, electric basses, electric banjos, electric pedal steel guitars, electric violins, etc. While directly applicable to traditional electric instruments and that is the primary focus of the invention, the concept can be applied to traditional acoustic stringed instruments, such as violins, cellos, pianos, banjos, and acoustic guitars that have been equipped with electronic pickup systems.
This invention solves the unintentional pitch problems caused by pitch drift, and intonation errors. This invention also provides a fast and reliable way to apply intentional pitch alterations of an almost unlimited variety.
This invention equips the instrument with the Pitch Processing System. In the described main embodiment shown in
The transducer has a plurality of sensors. The transducer may comprise magnetic, optical, or piezoelectric types of sensors.
Each sensor in the transducer system is dedicated to an individual string of the instrument.
The role of the Pitch Processing Module 1 and software in this invention is to:
The Pitch Processing Module 1 uses digital signal processing techniques. Types of digital signal processing which may be used in the present invention include, but are not limited to, lowpass filters, bandpass filters, highpass filters, multiplexing and demultiplexing, and Fast Fourier Transforms.
The Pitch Processing Module 1 will have been programmed a priori with data in lookup tables in its memory system to determine the correct pitch for notes played, and to apply the appropriate pitch alteration.
There are five components of pitch alteration used by the Pitch Processing System:
Electric instruments generally require external amplification for sound reproduction. Refer to
Interpreting the Memory Lookup Tables:
Refer to
The first two columns labeled “Note name*” and “Fret position*” do not represent values in memory, but are shown in the illustrations as cross reference aids and to ease readability of the tables.
The column labeled “FR” contains the reference fundamental pitch in units of Hz (Hertz) of each note on the string.
The table in
As indicated by the table:
In
The pitch altering lookup tables, which may reside in memory integral with the processor 7(
The transducer 3(
Refer again to
The processor 7 operates by analyzing the multiplexed digital data 25 in a manner such that the plurality of input signal information is acted upon incrementally and in parallel in software.
The Pitch Altering Procedure:
Process 500(
FC represents a pitch deviation from the open unfretted ideal pitch value FR. If the value of FC is greater than the value zero, then the open unfretted note is flat, or lower than desired. If the value of FC is less than zero, the open unfretted note is sharp or higher than desired.
At 504(
Variable FALT will be used to accumulate a series of pitch alteration factors: pitch correction FC, real time pitch bend FDTREM, temperament and intonation adjustment FMOD, and pitch shift FSHIFT. FC, FMOD, and FSHIFT are derived from values stored in the memory table and a unique value of each can be defined for every note of the instrument. The FDTREM value, in this embodiment, is a variable calculated in 788(
At 506(
The decision at 510 allows an update to occur to the pitch correction value FC for this string, or the update can be disabled to accommodate an alternative embodiment.
If FC updating is enabled at 510, step 512 calculates a new FC value based on the current open string pitch FRT where FC=(FR−FRT)/FRT, and stores FC in the memory table
If it is determined that this was not an open unfretted note at step 506, a reverse lookup content search at 513a is performed on TBL[5] in
A variety of methods could be used to perform the reverse lookup at step 513a. Since the TBL[5] array is small, limited by the number of frets on the instrument (guitars typically have 21 or 22 frets) a simple divide and conquer approach can be used for this discussion. In the reverse lookup, the value F1 calculated in 504(
When the closest match is determined, the resulting row index used in the search is equal to the row number of the table, and is equivalent to the fret number corresponding to the position of the note played. At step 513b, the nFRET variable is assigned the value of the row index returned from the search in 513a. Assume the value of nFRET is decimal 10 for this discussion. Also in 513b, variables FMOD and FSHIFT are assigned values of zero for this note from the table locations TBL[5][10,2] and TBL[5][10,3] respectively.
If so enabled at step 516, the pitch correction value 1+FC is assigned to variable FALT in step 518. If enabled at step 520, FALT is multiplied by the pitch bend value 1+FDTREM in step 521, and saved in FALT. If enabled at step 522 FALT is multiplied by the temperament or intonation adjustment value 1+FMOD at step 526 and saved in FALT. Lastly, if enabled at 528, FALT is multiplied by the pitch shift value 1+FSHIFT at 532 and saved in FALT.
A sanity check step is applied at step 533 to check whether the value of the cumulative pitch alteration factor FALT is of sufficient magnitude to process a pitch alteration. If FALT is within range of an implementation defined threshold, no processor resources need to be expended to perform a pitch alteration for this sample.
Step 534 initiates the computation to pitch alter the digital signal from the current string using the cumulative pitch alteration factor FALT. In this process, FALT has been calculated from four pitch alteration factors as:
FALT=(1+FC)*(1+FDTREM)*(1+FMOD)*(1+FSHIFT)
Using well known digital pitch altering algorithms, the digital signal buffered in memory is resampled, and adjusted for pitch using the value of FALT. The target pitch required is expressed as FRT*FALT. If the resulting value of FALT is greater than 1.00, then the pitch will be increased. If the resulting value of FALT is less than 1.00, then the pitch will be decreased.
At step 536, statistics regarding the pitch drift of the instrument can be generated and stored in memory for later analysis. Also, an indication can be sent to the display 23(
After pitch altering is performed in process 500(
Active Calibration is accomplished using the logic path 550(
There is flexibility in allocating the pitch correction factors in the memory table
A good reason to grow the size of the TBL structure might be to allocate more entries to statistics such as “the number of times this note was played” which, along with similar statistics from the other note positions, could be used to estimate when it might be time to change strings.
The Calibration Process:
The calibration process 660(
The processor's software is placed in calibration mode by means of a control 18–21 and 165(
Step 6677 determines which reference pitch to use for this string, depending on whether the user selected a standard or chromatic pitch reference. Using standard guitar pitch (E, A, D, G, B, E), step 668 will lookup a reference standard pitch value from table CAL[ ] shown in
The musician tunes the instrument using the mechanical tuners 24(
Once the procedure is complete, the musician causes the processor to exit calibration mode by means of a control input or command causing the software to switch out of the calibration process at step 672(
Note that the pitch of a string adjusted by the user in process 660(
Tuning to an altered chromatic pattern, such as detuning a guitar one semitone to Eb from E, requires that the FR values in the lookup table be programmed to this Eb reference. These values are calculated in 6678(
The FR values that result from calibration will always reference the absolute pitches the musician has tuned the strings to, regardless of any other pitch alteration factors that may be stored in memory.
When switched to normal operation, the processor will continuously execute process 500(
Applying Intonation Compensation and Temperament Adjustments:
Intonation compensation and temperament adjustments are accomplished in an almost identical fashion, so they are described here together. The FMOD value is retrieved from the memory table
In
Applying Pitch Shifting:
Pitch Shifting is accomplished by retrieving the FSHIFT value from the memory table in step 513b(
The process 750(
Interesting and advantageous altered pitch configurations can be easily applied to the instrument by applying a pitch shift map to alter the memory lookup table. The following examples will show some of the more useful variations.
A “Virtual Capo” example is shown in
A baritone guitar example is shown in the table of
A hybrid example is shown in the table of
Another hybrid example is shown in the table of
Applying Pitch Bending:
Pitch bending is accomplished by multiplying FALT by the value 1+FDTREM at step 521(
Pitch bending is accomplished when a pitch bend sensor device responding to touch input is activated. The touch input device shown as 165(
In step 788, the value of the pitch bend variable FDTREM is changed based on the sensor type and its current value, and then the process terminates.
If ACTIVE is true, step 786 then determines if the sensor is no longer in use. If the sensor is no longer in use, step 790 will change the ACTIVE variable to false indicating that there is no sensor event in progress, resets the FDTREM variable to zero, and then the process terminates.
Tracking Fingered Pitch Dynamics:
When a musician is using pitch altering techniques such as string bends, vibrato, or other pitch dynamics using fingered techniques, the process 500(
Description of Alternative Embodiment 1:
In an alternative embodiment applied to conventional electric stringed instruments such as electric guitars and basses, the sound from the existing magnetic pickups can be preserved. Many guitarists prefer certain instruments models and brands for the characteristic sound of their magnetic pickups.
Traditional magnetic pickups are shown as 850 and 852 (
Alternative Embodiment 2:
In an alternative embodiment, a control can be employed to allow the musician to enable or disable Active Calibration.
A control 18–21 and 165(
Alternative Embodiment 3:
In an alternative embodiment, additional digital audio processing can be performed by the Pitch Processing System. Examples of this type of digital audio processing are applying effects such as equalization, echo, flanging, and distortion. The processor and software, possibly in combination with option card hardware and software available over the adapter interface 160(
Alternative Embodiments 4 through 11:
Pitch altered instrument signal outputs can be presented to a variety of external interface types in several alternative embodiments of the invention. The following sections describe the embodiments as applied to the electric guitar. The input/output connector area of the guitar is typically located on the instrument edge shown as 101(
Alternative Embodiment 4:
In this embodiment, the pitch altered digital signals are summed together in a digital mixing process performed by the processor 7(
Alternative Embodiment 5:
In this embodiment, a plurality of analog signals, one associated with each individual string, is processed and sent to an analog output connector. The processor 7(
Alternative Embodiment 6:
In this embodiment, two separate analog signal outputs can present left/right stereo signals using a multiconductor ring-tip-sleeve connector and cable of the type shown in 10b(
The signals are processed in a manner that produces a left/right stereo image, for example to produce a stereo chorus effect. The processor then emits digital signals 150(
Alternative Embodiment 7:
In this embodiment, DC power input can be supplied to the Pitch Processing System using a multiconductor ring-tip-sleeve connector and cable of the type shown in 10b(
Alternative Embodiment 8:
In another embodiment, the instrument's pitch altered digital signals can be presented in a multichannel format wherein the pitch altered digital signals are separately presented to a plurality of external digital interfaces. One example of such an interface uses the six separate S/PDIF connections as shown as 15b(
Alternative Embodiment 9:
In another embodiment, the pitch altered digital signals may be multiplexed using a variety of techniques such as encoding, packet or cell multiplexing, or time division multiplexing to transmit the resulting data over an interface connection. This embodiment describes the use of the IEEE802.3 interface 14 (
Alternative Embodiment 10:
The pitch altered digital signals 150(
Alternative Embodiment 11:
In another embodiment, an adapter interface 160(
Alternative Embodiment 12:
This embodiment describes the use of data processing and transmitting data. Data gathered from the instrument may accompany the pitch altered digital signals. Bidirectional digital interfaces such as USB 12(
Alternative Embodiment 13:
This alternative embodiment describes the use of data processing and receiving data. External devices can send information to the instrument to be received by the Pitch Processing System to be acted upon in useful ways.
An external device can be connected to the instrument using one or more of the bidirectional digital interfaces shown as 12–16 and 160 (
Alternative Embodiment 14:
It should be clear to those familiar with the art to understand that the invention has many potential mechanical configurations. The partitioning of the electronic components based on the instrument's design may warrant different module configurations from those described in the main embodiment.
The display 23(
Alternate Embodiment 15:
This embodiment describes how intonation calibration can be used on a guitar or bass to program the memory table FMOD values to correct for intonation error.
An intonation calibration process 6600 is shown in
The difference between the open string pitch Fopen multiplied by two, and the twelfth fret pitch F12, is a measure of the twelfth fret intonation error. This calculation takes place at step 6632, is assigned to variable INT—CF and is expressed as a fraction either less than or greater than zero.
The intonation error for the fret positions 1 through 11 tends to be less than the twelfth fret error INT—CF. The intonation error for fret positions 13 through 21 tends to be greater than the twelfth fret error INT—CF. At step 6634, the twelfth fret error is amortized across all of the fret positions and FMOD values for each fret are calculated and stored in the table at step 6634. In this simple example, the calculation weights a greater error to the higher numbered fret positions. Other more sophisticated amortization schemes could be employed at step 6634 depending on specific implementation requirements.
The resulting FMOD values are shown in the memory table shown in
The intonation calibration process is terminated by the user activating a control 18–21 and 165 (
Conclusions, Ramifications, and Scope
The reader will see that the Pitch Processing System eliminates the major sources of pitch drift, and provides a reliable and sophisticated method of applying pitch alterations to electric stringed instruments. The invention manages the instrument pitch electronically without electromechanical devices required to adjust string tension.
A summary of the Pitch Processing System's broad advantages over the prior art:
The scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the many examples discussed in the specification.
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