WO2000045372A1

WO2000045372A1 - Automatic tuning system for use with an acoustic stringed instrument

Info

Publication number: WO2000045372A1
Application number: PCT/US2000/002119
Authority: WO
Inventors: Stephen J. Freeland; Neil C. Skinn; Steven H. Klein; Colin Kaminski
Original assignee: Transperformance, Llc
Priority date: 1999-01-28
Filing date: 2000-01-27
Publication date: 2000-08-03
Also published as: AU2974700A

Abstract

An acoustic stringed instrument with an automatic tuning mechanism is provided. The tuning mechanism (3) is mounted so that acoustic sound generation is substantially unaffected. In the preferred embodiment this is accomplished by use of an acoustic mount (1a) which suspends the tuning mechanism within the guitar body (20) without direct contact with the guitar body. In an alternative embodiment the tuning mechanism is directly attached to the guitar neck (10) or the guitar body in a location such that the sound quality of the instrument is not substantially affected.

Description

AUTOMATIC TUNING SYSTEM FOR USE WITH AN ACOUSTIC STRINGED INSTRUMENT

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to prior U.S. provisional application 60/117,553 filed January 28, 1999.

BACKGROUND OF THE INVENTION

While manually tuning a musical instrument can be a difficult and tedious process, in and of itself this might not be a sufficient motivation for developing an automatic tuning system. However, when, as often happens, a musical instrument needs to be tuned during a performance, having an efficient method for tuning the instrument becomes far more essential.

There are several reasons that a musical instrument might need to be tuned during a performance. One reason might be a string breaking during the performance. Another reason might be that a capo, which is a device for clamping all strings to a particular fret, is being used. Yet another reason for re-tuning being necessary might be a change in environmental conditions, such as a change in temperature or humidity. All of these conditions would require re-tuning the musical instrument as all of these affect the frequency produced when a string is played. Finally, the performance might require the re-tuning of the instrument in order to play in a different tuning configuration.

One solution that is often used is that of having several musical instruments, which are properly tuned for these different situations, available. While this is a workable solution, one can easily see that it is expensive and inconvenient. A better solution is to be able to quickly tune the musical instrument.

Manually tuning the instrument takes time and skill, in addition to testing the instrument by playing and listening to the tuned strings. This is obviously not appropriate during a performance. Automatically tuning the instrument is quick and requires at most a single strum. Obviously, automatically tuning a musical instrument provides a better solution.

Many different types of automatic tuning systems have been devised that work with electric (non-acoustic) instruments. The present inventors have devised a system that automatically tunes an electric instrument using a calibration function, as described in U.S. Patents No. 4,803,908, No. 4,909,126, No. 5,824,929, No. 5,859,378 and U.S. Patent Application No. 08/680,725 filed July 12, 1996, which are incorporated herein by reference for their teachings of the components of the tuning system. To install an automatic tuning mechanism into a solid body electric instrument, generally a cavity is cut into the face of the instrument.

However, we are not aware of any automatic tuning systems that work with acoustic stringed musical instruments. The main reason for this is that in an acoustic stringed musical instrument, the form of the instrument is integral to the quality of the sound produced. For example, were an object placed on the face of a guitar, the sound produced when the instrument is played would suffer both a loss in volume and a loss in richness through the loss of lower order harmonics.

It is for this reason that, while there have been many devices invented for automatically tuning a non-acoustic instrument, so far the possibility of achieving this in acoustic stringed musical instruments such as acoustic guitars has been dismissed.

In addition to having to fill the requirement of not significantly damping the vibrations of portions of the instrument's body resulting from strings being played, an automatic tuning system for an acoustic stringed musical instrument would preferably compensate for all the other variables already mentioned, namely the installation of a capo, the breakage of a string, etc. In addition, it is known that there are interactions between the strings of a musical instrument that are preferably taken into account when tuning it. It is the object of this invention to provide an automatic tuning system for an acoustic stringed musical instrument that will not significantly damp the sound produced when the instrument is played.

SUMMARY OF THE INVENTION This invention provides an acoustic stringed instrument with an automatic tuning mechanism. The tuning mechanism is mounted so that acoustic sound generation is substantially unaffected. In the preferred embodiment this is accomplished by use of an acoustic mount which suspends the tuning mechanism within the guitar body without direct contact with the guitar body. In an alternative embodiment the tuning mechanism is directly attached to the guitar neck or the guitar body in a location such that the sound quality of the instrument is not substantially affected. For example, in the case of a guitar it is mounted on the side or bottom of the guitar body rather than on the face.

The acoustic mount is a structure which is connected to the tuning mechanism and also connected in one or more places to the guitar body. It is preferably made of a rigid wood such as cherry, oak or maple. It can also be made of another rigid material such as plastic or metal. The acoustic mount is preferably connected to the guitar body at a location which is not crucial to sound generation. It is preferably connected to the instrument using screws, but it can also be attached by other means, such as adhesive or nails. In a preferred embodiment, it is connected on one end to the neck block and on the other end to the end block. Most preferably it is connected to the upper portion of the neck block and the lower portion of the end block. The tuning mechanism is connected to the acoustic mount and is not in direct contact with the guitar body. There are numerous configurations of acoustic mounts which can provide this function. In each configuration the mount is preferably connected to the neck block, the end block, or to a brace within the guitar. These structures are less crucial to sound generation than the front or back face of the guitar. The acoustic mount can be connected to a lower portion of the neck block and an upper portion of the end block, or to central portions of each so that the acoustic mount is parallel to the front or back face of the guitar. The acoustic mount can be attached solely to the guitar back or solely to the end block. The primary criterion for positioning the acoustic mount is that it does not rest on a portion of the guitar which is crucial to sound generation. A clearance hole us used for connection of the strings to the tuning mechanism. This clearance hole can be used to change a string.

Alternatively, the tuning mechanism can be mounted directly to the guitar body. Again, it is preferably connected to braces or end blocks rather than the faces of the guitar body. It is most preferably connected to the end block, the neck block or the back or sides of the guitar body. It is preferably connected by screws, but it can be connected by other means such as adhesives, nuts and bolts, or nails. At this time, the size and weight of the tuning mechanism is too great to directly attach it to the front face of the guitar without compromising the sound of the guitar. If the features of automatic tuning are considered more important than the sound quality of the guitar, then the tuning mechanism could be attached to the face of the guitar or, if the actuators in the tuning mechanism were miniaturized such that it became light enough not to interfere with sound quality, it could be so mounted on the face of the guitar. Presently it is considered preferable to mount it to some portion of the guitar body or to the guitar neck, rather than the face of the guitar.

The tuning mechanism comprises at least one actuator connected to at least one string of the stringed instrument. Preferably when there is a plurality of strings, there is one actuator connected to each string. In order to tune the instrument the actuators are used to change the tension on the strings and thereby change the frequency produced by the strings. Any of the many actuators known in the art can be used. The actuator can comprise a stepper motor, for example, connected to the string either directly or via gears or levers, or the actuator can employ any of the many other motors known to the art. There are many types of actuators adaptable to tuning an instrument, including electromechanical devices such as stepper motors, servo motors, linear motors, gear motors, leadscrew motors, piezoelectric drivers, shape memory metal motors, and various magnetic devices. Position reference devices for actuators include electrical contacts, optical encoders and flags, potentiometers, and mechanical stops for stepper motors.

The tuning system also comprises one or more transducers which are coupled with the strings. A plurality of different transducers are suitable for use in the tuning system. They can be acoustically coupled with the strings. An example is a microphone. In this case, if a plurality of strings are sounded simultaneously, as in the preferred embodiment, then the frequencies of the individual strings must be separated out. This can be done with a plurality of bandpass filters or with a Fourier transform. The term "transducer" is used herein for any device for providing a signal from which the frequency can be obtained. Examples include microphones, optical sensors coupled to vibrating elements and strain gauges measuring tension in strings of stringed instruments, as well as magnetic or electric field sensing devices coupled to vibrating elements of an instrument. The transducers can be alternatively coupled with the strings. In this case, there is one electrical transducer for each string. The frequency of the string can be obtained by zero crossing period counting. The transducer can also be mechanically coupled with the string. For example, a piezo electric transducer (PZT) can be positioned in contact with each string to obtain the frequency of the string, or a single PZT can be used coupled with the bridge to pick up the combined frequency of all the strings. In this case, again, the individual frequencies need to be deconvoluted.

The tuning system further includes a controller. The controller is used to take the signals from the transducers and convert them into the frequencies of each of the strings. The controller also contains a comparator or some kind of calibration means for comparing the measured frequency with the desired target frequency and then generating a control signal corresponding to the difference. The control signal is sent to the actuators to correct the frequency of each string. In the preferred embodiment, the controller utilizes a calibration function to calculate the desired actuator signal. The calibration function relates the frequency of each string with the actuator position of that string. Preferably it takes into account the actuator position or the frequency of all the strings. Because there is an interaction between the tension on each string and the tension on the other strings, the preferred calibration function is described in U.S. Patent No. 5,824,929. The controller can include a library of calibration functions. Each calibration function is appropriate for use in a different instrument configuration. For example, when a capo is installed on an instrument, the frequency of a given string as a function of actuator position is changed and so a calibration for each capo position can be included. Further, calibration functions for a broken string can be included. When a string breaks, the loss of tension on that string affects the tension on all the other strings and therefore affects the calibration function for each of the strings. The calibration library can also include changes in string gauge or other operating conditions, different bridges, and/or different mechanical configurations of the actuators.

In addition to a tuning system adapted for use with an acoustic stringed instrument, this invention also provides automatically tuned acoustic stringed instruments including the tuning system. The self-tuning acoustic stringed instrument includes an acoustic stringed instrument and further includes a tuning mechanism mounted thereon. The tuning mechanism can be mounted with an acoustic mount or can be mounted directly on the instrument. In order for a string to be connected from the bridge to the tuning mechanism there is generally a string clearance hole or a plurality of string clearance holes within the face of the guitar. The string stretches from the bridge of the instrument to the tuning mechanism within or on the outer surface of the instrument. A single clearance hole can be used through which all the strings pass to the inside of the body of the stringed instrument. The clearance hole can be of any shape; for example, it can be rectangular or round. Preferably it is as small as possible to allow the strings to pass to the tuning mechanism. Rather than a single clearance hole for all the strings, each string may have its own clearance hole drilled into the face of the guitar. In one embodiment the strings go vertically down from the bridge to the tuning mechanism within the guitar. In this case the clearance holes can be drilled in the bridge.

The stringed instrument can further include an access hole in the body of the instrument to allow maintenance of the tuning mechanism. Such an access hole can be made in a conventional acoustic instrument to allow retrofitting of a tuning system, or acoustic instruments can be fabricated initially with such access holes and with automatic tuning systems installed. The access hole can be positioned in the back of the instrument, on the side of the instrument, in any position that allows access to the tuning mechanism. The tuning mechanism can be removed for maintenance but is preferably maintainable in its position within the guitar. The access hole can be covered with a cover panel when the instrument is being played. In one embodiment, the tuning mechanism is externally mounted on, for example, the heel of the neck or on the end of the guitar. In this case, an access hole is not required.

To route the strings within the guitar from the bridge to the tuning mechanism or from the tuning mechanism to the mount, roller bridges can be used. The advantage of roller bridges is that the tension of the strings can be adjusted with minimal friction. In one embodiment, the saddle of the bridge is replaced with roller bridges, one for each string, which then direct the strings through the clearance hole(s) to the tuning mechanism. In another embodiment the neck of the instrument is hollow and the strings travel from the mount through the neck to the tuning mechanism.

The self-tuning acoustic stringed instrument can further include one or more transducers to obtain the frequency of each string. The frequency of the string is proportional to the tension, and so adjustment to the tension is used for tuning the instrument. The self-tuning instrument also includes within the tuning mechanism actuators for adjusting the tension on each string. The instrument can also include a controller to receive the transducer signal and to send a control signal to the actuators. The controller can use a calibration function.

The preferred tuning procedure is as follows: the musician determines that the instrument requires tuning or a check of the tuning. A single strum of the strings can obtain the frequencies of all the strings by using, for example, separate transducers for each string or a Fourier transform to separate out the frequencies. These frequencies are then compared to the target frequencies. The difference between the actual and target frequencies can be used to "touch up" the tuning, which is to say, to correct the calibration function and make it correspond to the actual string condition at the time. The strings after the single strum can then all have their tensions adjusted so that their correct frequencies are received. The calibration function is then updated so that the current instrument conditions are reflected by the calibration function. In the preferred embodiment of the control system utilizing a calibration function, the tuning can be automatically changed from one tuning configuration to another, for example, from standard tuning to open G tuning, without even strumming the strings. Because there is a calibration function which provides the correct actuator position for each frequency of each string, the strings can be automatically changed from one set of frequencies to another. If the instrument is in tune for a first set of frequencies, then the strings can all be simultaneously tuned to another desired set of frequencies, e.g., to change key. This invention is particularly useful for musicians who use different tuning configurations in the course of a performance, for example those who play the banjo or guitar. However, for bass players, for example, the musician may want to only change the tuning on the E string. The calibration library can allow this.

This invention further includes a method of tuning an acoustic stringed instrument. The method comprises providing an acoustic stringed instrument having a tuning mechanism attached thereto, with a transducer coupled with the strings, a controller coupled with the transducer and with actuators on the tuning mechanism. The method further comprises strumming, or in some way sounding, the strings of the instrument such that the transducer generates a transducer signal indicative of the frequencies of each string, the controller receives the transducer signals and generates from the transducer signals actuator (control) signals and sends them to the actuator which adjusts the tension on each of the strings to produce the desired frequencies.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

Throughout this document the following definitions apply :

acoustic mount: a device connected to a tuning mechanism and to the body and/or neck of an acoustic stringed instrument so that the tuning mechanism is suspended within the body.

acoustic stringed musical instrument: a stringed musical instrument not dependent solely upon electrical sound generation. Sound is produced by mechanical means.

actuator: an electrical device and associated mechanical components that adjust the tension of a string.

back: the back of a musical instrument includes the braces and surface of the back portion of the instrument opposite the strings.

calibration function: any function relating the frequency of one or more strings to the actuator position of a string.

calibration library: a plurality of stored calibration functions. instrument condition sensor: a device for detecting one or more of a variety of conditions including: temperature, humidity, presence of a capo, one or more broken strings.

target frequency: the desired frequency of a string.

transducer: a device for measuring, with a controller, the frequency produced by one or more strings. This device can be, for example, an electric pickup, a microphone, a PZT, or a string gauge to measure the tension of a string.

tuning configuration: a set of target frequencies, one per string.

tuning mechanism: a device comprising one or more actuators.

BRIEF DESCRIPTION OF THE DRAWING Figure 1, comprising Figures 1A-B, is a schematic of (A) a cross section and

(B) a top view with the top surface removed of a self-tuning guitar having an acoustic mount attached to the top of the neck block and the bottom of the end block of the guitar.

Figure 2 is a schematic of a cross section of a self-tuning guitar having an acoustic mount attached to the end block of the guitar.

Figure 3 is a schematic of a cross section of a self-tuning guitar having an acoustic mount attached to the inside back surface of the guitar.

Figure 4, comprising Figures 4A-B, is a schematic of (A) a cross-section and (B) a top view with the top surface removed of a self-tuning guitar having an acoustic mount attached to the sides of the guitar. Figure 5, comprising Figures 5A-B, is a schematic of (A) a cross-section and

(B) a top view with the top surface removed of a self-tuning guitar having an acoustic mount attached to the middle of the neck block and the middle of the end block of the guitar.

Figure 6, comprising Figures 6A-B, is a schematic of (A) a cross-section and (B) a top view with the top surface removed of a self-tuning guitar having an acoustic mount attached to the bottom of the neck block and the top of the end block of the guitar.

Figure 7 is a schematic of a cross section of a self-tuning guitar having the tuning mechanism attached to the back surface of the guitar.

Figure 8 is a schematic of a cross section of a self-tuning guitar having the tuning mechanism attached to the end block of the guitar.

Figure 9 is a schematic of a cross section of a self-tuning guitar having the tuning mechanism attached to the neck block of the guitar.

Figure 10 is a schematic of a cross section of a self- tuning guitar having the tuning mechanism attached to the outside of the end of the guitar.

Figure 11 is a schematic of a cross section of a self-tuning guitar having the tuning mechanism attached to the heel of the guitar.

Figure 12 is a schematic of a top breakaway view, with part of the top surface open, of a self-tuning guitar having the tuning mechanism attached to the inside surface of a side of the guitar. Figure 13 is a schematic of a cross section of a self-tuning guitar with a hollow neck having the tuning mechanism mounted on the neck and the strings routed through the hollow neck using string-routing members.

Figure 14 is a schematic of a cross section of a self-tuning guitar with a hollow neck having the tuning mechanism mounted on the neck and the strings routed through the hollow neck using levers.

In the discussion of the drawings that follows, the same number that appears in more than one drawing refers to the same element. Similar number refer to similar elements.

In a preferred embodiment, the acoustic mount supports a tuning mechanism within the body of the instrument and the acoustic mount may be connected to the tuning mechanism and to the side, front or back surface of the guitar or to the neck of the guitar. The tuning does not rest upon the guitar itself but is suspended with at most one edge of it, or two edges of it if it is in a corner, and does not come into contact with the body of the guitar. The acoustic mount is made of a material that is preferably lightweight, rigid and reduces acoustic contact between the tuning mechanism and the guitar body. Preferably rigid wood such as cherry, oak, or maple is used, but plastic or metal can also be used. The acoustic mount can also be a plurality of cables stretching across the body of the instrument. A key feature of the acoustic mount is that it allows a bulky or heavy tuning mechanism to be attached to the body or neck of the guitar without substantially damping the acoustic properties of the instrument. This invention applies to any acoustic stringed musical instrument. As a shorthand in this discussion and in the drawings, the word guitar is used to represent any instrument. The judgement of the musician can determine if the acoustic property of the guitar is substantially damped. However, if the sound is measured by a voltage meter and a spectrum analyzer, it is considered substantially undamped if the sound, as measured by the voltage analyzer, is not lessened by more than 6 decibels (dB) but preferably less than 2dB, and if, when viewed by the spectrum analyzer, the second and third order harmonics are not lost.

Figure 1 is an embodiment of the acoustic stringed instrument of the present invention with a tuning mechanism therein. Tuning mechanism 3 is suspended within the instrument on acoustic mount la. On the body 20 is an end pin 6 and an end block 16. The neck 10 is attached with a dovetail joint 18 to the body 20. This is a typical, although not necessary, attachment for a guitar. The dovetail joint 18 attaches the neck 10 to neck block 14. It is typical for a guitar to have an end block and a neck block and to further have a plurality of braces on the inner portion of the guitar. The back of the guitar, for example, generally has a number of cross braces attached to it. The term "back" is used for both the braces and the shell of the guitar opposite the strings. Similarly the term "sides" is used for any braces that might be on it the sides, including the neck block 14 and the end block 16 as well as for the shell of each side. The term "front" or "front face" of the instrument is used for the shell of the front (the side on which the strings are played) including any braces or blocks that may be attached thereto.

Figure 1A is a cross-section of the guitar. It shows the heel 12 of the neck 10. It also shows tuning mechanism 3 suspended within the guitar body. The acoustic mount la is attached to an upper portion of the neck block 14 and it is also attached to a lower portion of the end block 16. It is not necessary that the attachment be as illustrated. Acoustic mount la may be attached to any point on the end block 16 and neck block 14.

Figure IB is a top view of the instrument with the front of the guitar removed so as to reveal the inner elements. Acoustic mount la is connected to tuning mechanism 3 and to end block 16 and the neck block 14. In Figure 1 A a single string 2 is shown to illustrate how the string 2 goes over the bridge 4 to the tuning mechanism 3. Although a single string 2 is illustrated, the acoustic stringed instruments of this invention typically have a plurality of strings, four strings for a cello, viola or violin, five strings for a banjo, six strings for a guitar, eight strings for a mandolin, or however many strings the particular instrument has. Clearance hole 17a within the surface of the instrument allows routing of the strings from bridge 4 to tuning mechanism 3. While it is possible to wrap the strings through the sound hole (not shown) of the instrument, it is much more direct in this embodiment to include a string clearance hole 17a. The hole 17a can be a single hole through which all the strings pass or there can be one hole drilled for each string. Tuning mechanism 3 comprises an actuator (not shown) for each string. The actuator serves to change the tension on the particular string.

There are many types of actuators adaptable to tuning an instrument, including electromechanical devices such as stepper motors, servo motors, linear motors, gear motors, leadscrew motors, piezoelectric drivers, shape memory metal motors, and various magnetic devices. Position reference devices for actuators include electrical contacts, optical encoders and flags, potentiometers, and mechanical stops for stepper motors. Many other types of apparatus will be obvious to those skilled in the art of control systems. A preferred embodiment includes the choice of an actuator which holds its position when power is removed; for example, a stepper motor or a gear ratio, leadscrew pitch, lever arm, or ramp with a critical angle such that if the motor produces no torque the tuning does not change. The motors can be connected to the strings by directly attaching a string to a motor shaft, or by various mechanical systems utilizing components such as gears, roller bridges, springs and levers. The actuator can change the tension on the string by pulling along the axis of the string or by transverse deflection of the string. Many mechanical actuators for altering string tension have been described in the art. The control system of the present invention can be employed with any actuator. Each string can have more than one actuator attached to it, for example for coarse and fine control of the string frequency. A second embodiment of the acoustic mount is shown in Figure 2. In this embodiment, mount lb is attached to the end block 16 of the instrument and curves around to support the tuning mechanism 3.

Yet another embodiment of the acoustic mount is illustrated in Figure 3. Mount lc is attached only to the back of the guitar, preferably to braces on the back of the guitar. Although it can alternatively be attached directly to the shell, in this cross- section of Figure 3 we see the edge of the acoustic mount. This acoustic mount has two upright portions, one closer to the neck and one closer to the end.

Figure 4 shows yet another embodiment of the acoustic mount. In this illustration the acoustic mount Id is connected to the sides of the guitar. Tuning mechanism 3 is suspended within the body of the guitar. The cross-section of Figure 4A shows the acoustic mount at an angle with respect to the front surface of the guitar. This is preferred for receiving the tension of the strings.

Figure 5 shows an embodiment where the acoustic mount le is connected to center portions of the end block 16 and the neck block 14 and is approximately parallel to the front of the guitar. In Figure 5B the top view shows tuning mechanism 3 positioned on the acoustic mount le.

Figure 6 shows an embodiment in which the acoustic mount If is connected to an upper portion of the end block 16 and a lower portion of the neck block 14. The top view of Figure 6B shows tuning mechanism 3 positioned on the acoustic mount If.

Another preferred embodiment of the guitar uses an acoustic mount upon which the tuning mechanism is suspended within the guitar body. It is also possible to attach the tuning mechanism directly to the guitar body. It is preferably positioned upon the guitar body such that the acoustic vibrations of the guitar are not substantially impacted. For example, it can be positioned on the back or the side of the guitar with far less impact on the sound than if it were positioned on the front face of the guitar as is done with electric stringed instruments.

Figure 7 shows tuning mechanism 3 attached directly to the back of the instrument. It is preferably positioned on cross-braces of the instrument, but it can also be connected directly to the back shell of the instrument.

In Figure 8 tuning mechanism 3 is positioned on the end block 16 of the instrument. Because it is on the end block 16 which is more massive than the shell of the side of the guitar, it has less impact on the acoustic vibrations of the guitar.

In Figure 9 tuning mechanism 3 is attached to neck block 14 of the instrument. Neck block 14 which adjoins neck 10 is perhaps the most massive element within the guitar body. Because of this, positioning the tuning mechanism 3 on the neck block 14 has less impact on the acoustic vibrations of the guitar. In order to route strings 2 from bridge 4 to tuning mechanism 3, a string-routing member 5a is used. The string- routing member may be a roller bridge or other grooved member mounted in place via a mounting means such as a screw, wire or acoustic mount as described herein. If in the form of a wheel, it may be rotatably mounted. The function of the string-routing member is to route the strings without creating friction. Friction would cause the actuator in tuning mechanism 3 to work harder and to require greater power and perhaps greater weight. The string-routing member 5a also provides smooth motion of the strings 2 as opposed to jerky motion. The tuning mechanism can alternatively be mounted on the outside of the guitar so as to provide easier access to the tuning mechanism for maintenance or for string changing. Ordinarily, the string is changed through the clearance hole or acoustic hole. A ball or other connector can be attached to the end of a string attached to the tuning mechanism, which can be used to connect the string to the tuning mechanism. The string is dropped through the hole and the connector at its end is used to attach the string to the tuning mechanism. In Figure 10 tuning mechanism 3 is positioned at the outside surface of the guitar. String clearance holes 17b are formed in the side of the guitar to allow routing of the strings from bridge 4 to tuning mechanism 3.

Figure 11 illustrates the tuning mechanism 3 mounted on the heel 12 of the guitar. In order to route the strings 2 to the tuning mechanism 3 on the heel of the guitar, string-routing member 5b is used. Clearance hole 17a in the front of the guitar is used. In addition clearance holes 17c through the side of the guitar, the neck block 14, and the heel 12 of the neck 10 are required.

In Figure 12 tuning mechanism 3 is attached to the side of the guitar. In order to route the strings 2 to the tuning mechanism 3, string-routing member 5c is required.

An alternative way to route the strings is through the neck of the guitar as opposed to through the body. Figure 13 shows the guitar with a hollow neck 10 to allow clearance for the strings 2. In this case, the string is shown anchored at bridge 4. It then slides over nut 8 into neck 10. In order to route the string from nut 8 to tuning mechanism 3, a string-routing member 5c is used. Tuning mechanism 3 is attached to the neck block 14 of the guitar. String clearance holes 17d through the side of the guitar and the heel 12 of the neck 10 are required to route the string. No string clearance hole in the front face of the guitar is necessary.

In lieu of string-routing member 5c shown in Figure 13, lever 9 can be used to route the strings as shown in Figure 14.

A complete tuning system comprises the tuning mechanism and it further comprises a transducer or a set of transducers to generate a signal indicative of the frequency of each string Some of the embodiments described herein are preferable for certain applications and instruments. For example, when using the automatic tuning system with a banjo, then it is undesirable to have the clearance holes on the front surface of the banjo. The choice of embodiment depends on the instrument.

Devices for providing a frequency signal include transducers sensitive to sound waves such as microphones, or magnetic or electric field-sensing devices coupled to vibrating elements of an instrument, optical sensors coupled to vibrating elements, and transducers sensitive to frequency-related phenomena such as strain gauges measuring tension in strings of stringed instruments. The term transducer is used herein for any device for providing a signal from which the frequency can be obtained, not limited to the examples cited above. The term transducer is used in the singular to refer to one or a plurality of transducer devices coupled to the strings. Depending on the particular transducer, the coupling to the strings can be, for example, mechanical, electrical, optical, through sound waves, or through a magnetic field.

The transducer can alternatively measure the tension of the strings rather than the frequency of the strings. The tension is proportional to the frequency and can be used as a frequency indicator. The tuning system further uses a controller to receive the transducer signals and to send the signals to the actuators. The transducer signal is generally converted into a frequency signal.

Frequency-measuring techniques include timers measuring the periods of signals, such as digital counters implemented in either hardware or software, or digital counters counting the number of cycles of a signal in a period of time. Other techniques include the use of Fourier transforms or other processing algorithms, analog or digital filters, and digital signal processors.

In the preferred control system, a controller compares the frequency of the strings to a target frequency, and directs an actuator to bring the frequency into accordance with the target frequency. The preferred way to do this is using a calibration function which relates the frequency of a given string to a corresponding actuator position. The calibration function most preferably relates the frequency of a given string and the frequencies of the remaining strings to a coπesponding actuator position for a string.

The prefeπed embodiment using a calibration function can further have a library of calibration functions stored in the control system. Each calibration function can correspond to different instrument conditions, for example, presence of installed capo, a broken string, or changes in the climate. The device can further include an instrument condition sensor.

Instrument condition sensors for detecting changes in operating conditions include force, pressure, and strain sensors for measuring string tension, thermistors for measuring temperature, various types of humidity sensors, current sensors for measuring electrical continuity or electrical contact between a string and a fret, and various types of electric or magnetic field sensing devices for detecting the presence of a string or capo.

This invention further includes a method of automatically tuning an acoustic stringed instrument. The method comprises the following steps: first, cause the strings to vibrate. This can be done by strumming, plucking, bowing or whatever might be appropriate for the instrument. A transducer senses the vibrations, or senses the tension of the strings in which case it is not necessary to strum the strings, and creates a signal which is indicative of the frequency of the strings. A controller receives the transducer signal and further generates an actuator signal which is sent to a tuning mechanism mounted within the guitar. The tuning mechanism can be mounted on an acoustic mount which suspends the tuning mechanism within the body of the guitar. The tuning mechanism can be mounted directly on the body of the guitar, either internally or externally. The tuning mechanism can alternatively be mounted on the neck externally. The actuator adjusts the tension on the string to bring it into accordance with the target frequency.

This invention has been illustrated with a few preferred embodiments including several embodiments of the acoustic mount. Numerous other embodiments of the acoustic mount can be used to suspend the tuning mechanism within the body of an acoustic stringed instrument. The tuning mechanism has been illustrated positioned on a spots on the instrument body, internally and externally. Numerous other positions can also be utilized. A key feature is that the acoustic vibrations are substantially undamped by the tuning mechanism. The invention has been illustrated primarily for guitar. It is suitable for any acoustic stringed instrument. A few embodiments of actuators, transducers and control systems have been illustrated. Any actuator which adjusts the tension of the strings, any transducer which generates a signal indicative of the frequency of the strings, and any controller which receives the transducer signal and generates an actuator signal can be used. The many embodiments which will be readily apparent to those skilled in the art are within the range and scope of this invention. This invention is defined by the attendant claims.

Claims

CLAIMS:

1. A tuning system for use with an acoustic stringed instrument, said instrument comprising a body and a neck, said body having a front, a back, sides, a neck block and an end block, said neck having a plurality of strings positioned thereover, said tuning system comprising :

a tuning mechanism comprising an actuator adapted to be connected to a string of said instrument;

an acoustic mount connected to said actuator and adapted to be connected to said instrument.

2. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected to a front portion of said neck block and a back portion of said end block.

3. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected solely to said end block.

4. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected solely to said neck block.

5. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected to the back of said instrument.

6. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected to the sides of said instrument.

7. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected to a center portion of said front block and a center portion of said end block.

8. A tuning system in accordance with claim 1 wherein said acoustic mount is adapted to be connected to a back portion of said neck block and to a front portion of said end block.

9. A tuning system in accordance with claim 1 wherein said acoustic mount is made of wood.

10. A tuning system in accordance with claim 1 wherein said tuning mechanism comprises a plurality of actuators, each said actuator adapted to be coupled with one of said strings .

11. A tuning system in accordance with claim 1 further comprising a transducer adapted to be coupled with said strings.

12. A tuning system in accordance with claim 11 wherein said transducer is acoustically coupled.

13. A tuning system in accordance with claim 11 wherein said transducer is mechanically coupled.

14. A tuning system in accordance with claim 11 wherein said transducer is electrically coupled.

15. A tuning system in accordance with claim 11 further comprising a controller for receiving a transducer signal from said transducer and generating an actuator signal for said actuator.

16. A tuning system in accordance with claim 15 wherein said controller utilizes a calibration function to generate said actuator signals.

17. A self-tuning acoustic stringed musical instrument comprising :

an acoustic stringed musical instrument, said instrument comprising a body and a neck, said body having a front, a back, sides, a neck block and an end block, said neck having a plurality of strings positioned thereover;

a tuning mechanism connected thereto;

wherein said instrument is substantially undamped by said tuning mechanism.

18. A self- tuning acoustic stringed instrument in accordance with claim 17 wherein said instrument has one or more string clearance holes therein to allow routing of a string to said tuning mechanism.

19. A self- tuning acoustic stringed instrument in accordance with claim 17 wherein said instrument has been retrofitted to install said tuning mechanism.

20. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said instrument was originally fabricated to accommodate said tuning mechanism.

21. A self- tuning acoustic stringed instrument in accordance with claim 17 wherein said tuning mechanism comprises a plurality of actuators, one per string.

22. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said tuning mechanism is attached directly to the back of said instrument.

23. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said tuning mechanism is attached directly to the sides of said instrument.

24. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said tuning mechanism is attached directly to the neck block of said instrument.

25. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said tuning mechanism is attached directly to the end block of said instrument.

26. A self-tuning acoustic stringed instrument in accordance with claim 17 further comprising an acoustic mount connected to said tuning mechanism and said instrument.

27. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to said end block.

28. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to said neck block.

29. A self- tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to sides of said instrument.

30. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to back of said instrument.

31. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to a front portion of said neck block and a back portion of said end block.

32. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to a back portion of said neck block and a front portion of said end block.

33. A self-tuning acoustic stringed instrument in accordance with claim 26 wherein said acoustic mount is connected to a center portion of said neck block and a center portion of said end block.

34. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said neck is hollow and wherein said strings are routed through said neck.

35. A self- tuning acoustic stringed instrument in accordance with claim 34 further comprising a plurality of string-routing members, one per string, wherein said string-routing members are positioned to route said strings.

36. A self-tuning acoustic stringed instrument self- tuning acoustic stringed instrument in accordance with claim 31 further comprising a plurality of levers, one per string, wherein said string-routing members are positioned to route said strings.

37. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said body has an access port therein.

38. A self-tuning acoustic stringed instrument in accordance with claim 17 wherein said back is removable from rest of said body.

39. A self-tuning acoustic stringed instrument in accordance with claim 17 further comprising a transducer adapted to be coupled with said strings.

40. A self-tuning acoustic stringed instrument in accordance with claim 17 further comprising a transducer adapted to be acoustically coupled with said strings.

41. A self- tuning acoustic stringed instrument in accordance with claim 17 further comprising a transducer adapted to be mechanically coupled with said strings.

42. A self- tuning acoustic stringed instrument in accordance with claim 17 further comprising a transducer adapted to be electrically coupled with said strings.

43. A self-tuning acoustic stringed instrument in accordance with claim 17 further comprising a controller.

44. A self-tuning acoustic stringed instrument in accordance with claim 17 further comprising a display coupled with said controller.

45. A method for automatically tuning acoustic stringed instrument comprising the steps of :

providing an acoustic stringed instrument having a tuning mechanism connected to the strings thereof and having a transducer coupled to the strings;

strumming a string of said instrument such that said transducer picks up a signal from said string and produces a signal indicative of the frequency of said string which is sent to a controller which sends a control signal to said tuning mechanism.