MUSICAL INSTRUMENT

Abstract: A musical instrument is described, with strings (7) and an exciter (29) attached to the sounding box (3) of a musical instrument such as a guitar. Additional sounds may be played through the exciter (29) to excite the sounding box (3) to produce an acoustic output. A transducer (21) may pick up the sound and feed it through a processor (23) to enable the musical instruments to produce effects such as reverberation. The musical instrument may allow the sound emitted by the instrument itself to be changed electronically.

Description: TITLE: MUSICAL INSTRUMENT DESCRIPTION The invention relates to musical instruments, and more particularly to a stringed musical instrument employing a soundboard, such for example a piano, and/or having a sound box e.g. a guitar, violin and the like. Inherently a stringed musical instrument produces an acoustic output by excitation of the soundboard by string vibration to cause mechanical vibration in the, usually wooden, soundboard and acoustic waves in the air surrounding the soundboard . O90/03025 describes an electric piano in which the soundboard of the piano can be driven. The movement of the keys may be measured and a corresponding sound excited in the sound box. The description specifically excludes the possibility that the mechanical mechanism through the strings may be used to excite the sound box in addition to the electrical excitation. Other ways of producing sound are known. Best known are the conventional conical, pistonic loudspeakers in which a cone is driven by an exciter to produce sound. An alternative form of loudspeaker, with many advantages, operates using bending waves. Such a panel form loudspeaker is described in O97/09842, and can be included in electronic musical instruments, as explained in WO97/09857, which describes the use of such a loudspeaker in a digital piano. However, the above documents do not describe at all methods of electrically adjusting the sound of a musical instrument as it is being played, nor of providing additional sound to the sound through the instrument. If it is desired to adjust the tonal quality of an instrument, it is normally necessary to provide a microphone to capture the sound of the musical instrument as it is being played, and then to pass the electrical signal output by the microphone through a processor. The processor can add effects such as reverberation or delay. However, the processed electronic sound must then be listened to through headphones or loudspeakers - the modified sound is not produced by the instrument itself. There is thus a need for a way of modifying the sound output directly by an instrument. According to a first aspect of the invention there is provided a musical instrument comprising at least one string that can be vibrated to produce sound; a transducer for picking up electrical signals from the instrument; a processor for processing the electrical signal; a soundboard; and an exciter on the soundboard for exciting the soundboard with the processed electrical signal to produce an acoustic output. Using musical instrument according to the present invention the output sound of a conventionally played instrument may be adjusted as it is played. This may produce effects such as reverberation or delay The instrument may also be used to increase the volume of the instrument without the player having to play harder. This can be useful for subtle nuances such as playing natural string harmonics . With the technique according to the invention, acoustic musical instruments, e.g. hollow-bodied instruments, may be provided with processors built in to the instrument body, thus eliminating the need for an external amplifier-speaker combination to hear the processed signal. If reverberation is added to the fed- back signal, then the instrument may produce a sound, which would belie its size. Processors are already on the market with a vast array or different effects, and these could produce very different sounds when their output is fed through the instrument soundboard. Thus the technique described above may produce new and original sounds . Musicians often wish to play music accompanied by other musicians. However, in order to hear such other sounds signals additional loudspeakers or headphones are required. Alternatively, they may wish to listen to a drum or metronome beat while playing to develop . a sense of timing. Again additional equipment is required. The additional sound produced by such equipment is wholly separate from that produced by the instrument. According to a second aspect of the invention there is provided musical instrument comprising a soundboard, at least one string, the string being capable of being vibrated mechanically by a player of the musical instrument , a mechanical coupling mechanically coupling the at least one string to the soundboard, so that vibrations of the string are coupled to the soundboard to produce an acoustic output, an input signal connector for inputting an input signal to the musical instrument, and an exciter mounted on the soundboard and coupled to the input signal connector to excite the soundboard to produce sound corresponding to a signal applied to the input signal connector, so that the soundboard can be excited simultaneously by the exciter and the vibrations of the string to produce a combined output sound signal. An instrument capable of producing additional sound through the exciter permits sound such as backing tracks to be played through the instrument itself while the instrument is being played. Often, the vibrations produced by the music can be felt through the body, which helps the player feel closer to the music. This can also help feel the rhythm of a metronome beat . In the manner of some keyboard electronic instruments, additional voices or instrumental lines may be provided/selected or pre-programmed via a suitable interface, e.g. a MIDI. Thus the performer could have a backing track reproduced while playing the main tune on the acoustic section with or without electronic enhancement of that playing. Clearly the overall concept may provide limitless creative musical possibilities. The musical instrument may be a string instrument having at least one string that can be plucked or bowed to produce sound. "String instrument" is used here in the strict sense not including a piano, in which the strings are percussively struck. In the invention according to either aspect the exciter may be positioned on the body to achieve maximum or desired modal excitation density or desired sound character or quality as taught in WO97/09842. There may be a plurality of exciters. The transducer may be located on or adjacent to a string so that the original mechanical/acoustic signal from a stringed musical instrument can be directly processed and fed back to the soundboard of the instrument via the exciter so that a supplemental signal can be heard alongside the original signal . In the current trend for the signal processing of instruments such as string instruments, this may be used as an expressive tool to permit the use of the soundboard of the instrument to reproduce the effects of the processing. The need for an instrument amplifier to hear the processed signal is accordingly avoided. The mechanical vibrations of the strings of the instrument may be directly picked up and converted into an electrical signal by the transducer. By feeding back the signal to the soundboard of the instrument, the second signal will be present in the acoustic output of the instrument. As a result, the supplemental signal will be treated to the same coloration from the instrument body or soundboard as the original sound . The exciter may be an exciter of the general kind described in WO97/09842. The drive point for the exciter may be determined by experimentation and/or simulation. The function of exciter and transducer may be provided by a single transducer; any feedback may be reduced as discussed below. This may permit more accurate replay of sound. The sound can be recorded by the combined transducer and exciter acting as a transducer when the instrument is being played. Later, the same vibrations can be played back through the same combined transducer/exciter to accurately reproduce the sound of the instrument being played. The transducer may be a magnetic pickup. This has the advantage that it just picks up the movement of the vibrating string, not the sound on the soundboard. This can reduce effects of feedback which might otherwise arise. This may mean that the strings would have to be made using a ferro-magnetic material, e.g. steel. Applying this to an acoustic guitar, the problem here would be that the three thickest strings are generally constructed from bronze windings around a nylon core, while only the three thinnest strings are constructed from steel . The thicker strings would thus need to be modified to include a ferro- magnetic material. It may often be convenient for all the strings to be made of steel to allow such magnetic pick-up. However, with some instruments all steel strings may not be applicable. With a guitar the upper strings may be steel and the lower frequency strings may be tape wound in steel rather than the usual copper etc. Alternatively or additionally the processor may apply continuous pitch shifting ("warbling") to the signal, as an alternative approach to reduce feedback. The warbling may be at perhaps plus or minus 1% of the original frequencies. Alternatively or additionally, an algorithm in the digital domain may be used to minimise feedback resonance. Clipping may be applied to the fed back signal to limit any feedback to a predetermined level that does not intrude . Domestic hi-fi reproduction may also be provided by the device according to the invention. For example in the case of a violin, a full-range exciter placed in the violin body at a pre-determined position of optimum vibration could be utilised as a pickup. When a violinist plays a piece, the output could be amplified and recorded in a conventional way. Then the violin could be placed, preferably supported in the air at the same height it was at while played, and the signal played back through the same exciter. This would produce a sound very close to the original played piece. As another example, a piano may be provided with an exciter arrangement placed inside the body. A multi-track recording could be made using the exciters as mechanical - electrical transducers. Now a piano which is to be made to a smaller scale than the original with similarly scaled and placed exciters, can be used to play back the recording. This method might, when optimised, produce the played-back sound in the same way as the original, with the same colorations, timbre and acoustic wave transmission properties as the original. Thus, the musical instrument according to the invention may be capable of replaying a recording of itself with superior realism and fidelity since the vibrational and acoustic radiation properties of the original (or a similar instrument) are invoked. In the primary mode where the instrument body is excited it would, of course, be less suited to the reproduction of other sounds. In this operating mode the instrument itself is made the audio-reproducing device for the enhanced signal component, this duality further enhancing the instrument and the results that may be achieved with it. The processor may comprise a microprocessor. Aspects such as control of dynamic range within chosen or safe or prescribed limits, even user adjustable and the monitoring of feedback margin and its control e.g. by gain reduction frequency shifting and/or delay techniques may be allocated to the microprocessor with appropriate software programme, sensing and control circuitry. In this way the user/musician is freed from some of the difficulties which may arise from the introduction of excess positive gain to a looped transducer reproducer chain. Conveniently the microprocessor may incorporate or control signal processing section to provide a range of facilities for example delay, reverberation of various kinds, 'flanging 1 , echo harmonic multiplication, sub- harmonic generation (the latter to extend the low frequency behaviour and still more useful when a low range speaker is incorporated) bass enhancement by psycho-acoustically related harmonic synthesis. Additionally soft clipping may be incorporated for graceful overload characteristics, which may be deliberate aspect of sound quality control at the operating limit. Features such as frequency shaping and tone colour may be added . The microprocessor control may be by a wired interface or by radio or optical coupling and/or may be accomplished via a conveniently sited hard wired control panel on the body of the instrument, or a foot pedal unit. For reproduction, or for recording a pure or a mixed electrical signal, an electrical output may be provided. The output may include the transducer pickup signal component for later copying and or reproduction typically on conventional i.e. non- instrument -based loudspeakers. While the objective is not necessarily to make the instrument play louder, the effect of reverberation and additional voices will in fact have the effect of increased loudness and throw to an audience. Only moderate power may be required for a good effect, e.g. between 1 and 10 watts of rated power due to the exciter and radiation efficiency of the ensemble and the general loudness requirement. A built in battery may be provided to power the instrument for some applications. Conceptually the present invention creates a new musical instrument, self powered or locally powered which may or may not include additional loudspeakers, resonant panel or pistonic cone type, preferably with chassis decoupling so as not to unduly restrict the free natural vibration of the instrument. A cone loudspeaker may be installed to augment the low range frequency of the instrument and may work in conjunction with the enclosed volume and a port in the soundboard, known as a sound hole and having a Helmholtz resonance, thus providing for greater range and efficiency. For a better understanding of the invention, a specific embodiment will now be described, purely by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic drawing of a guitar according the invention, Figure 2 shows a top view of the guitar of Figure 1, Figure 3 is a schematic of the circuit used m the guitar of Figure 1, and Figure 4 shows a schematic of the use of the guitar of Figure 1 to play a backing track. A guitar (1) has a body (3) which acts as a soundboard, a neck (5) , and a plurality of strings (7) supported between a bridge (9) and the end of the neck (11) . The body (3) defines a sound hole (13) as is normal for guitars. In addition to the conventional components, a string motion pickup transducer (21) is attached to the body adjacent to the strings. Since the motion pickup (21) is mounted on the body, it picks up body vibration as well as motion in the strings. A processor (23) is provided within the body and electrically connected to the motion pickup (21) by electrical connectors (25) . The processor will not be further described since suitable processors are commercially available. A control panel (27) electrically connected to the processor (23) is mounted on the front face of the body of the guitar. The control panel provides controls to control the processor. Two inertial exciters (29) are mounted on the body (3) of the guitar; the exciters are commercially available exciters normally used for exciting distributed mode resonant bending wave loudspeakers . Both the control panel (27) and inertial exciters (29) are connected to the processor (23) by electrical connections (25) . A loudspeaker (31) is integrally mounted in the rear of the body (3) . A common connector (35) on the body provides signal input and output, and may be connected to a cable (33) that provides power input and signal input and output signal to the guitar (1) . Figure 2 shows a top view of the region of the guitar bridge (9) showing the location of the two exciters. Best results were obtained with the exciters positioned 10-20 cms away from the bridge (9) of the guitar on the opposite side of the bridge to the neck. The processing is illustrated in Figure 3. The vibration of the instrument strings and the mechanical signal from the instrument body are picked up by the motion pickup transducer (21) and processed in the processor (23) . These signals are then fed back to the instrument body (3) by means of the exciters (29) to produce enhanced effects. The rear loudspeaκer (31) may enhance the low frequency range of the guitar. Figure 4 illustrates schematically another use for the guitar, namely to play backing tracks or accompaniment. Musicians often wish to play along to a backing track, which is usually supplied from a stereo system using loudspeakers or headphones . A source (41) , generally a CD. player, is connected to an amplifier (43) . This transmits a signal through cable (33) to the instrument body (3) through the exciters (29) to excite the sound board to produce an acoustic output . This integrates the sound of the backing track with the instrument output . Tests have shown reasonable sound reproduction down to surprisingly low frequencies using this approach. Moreover, the vibrations produced by the music could be felt through the body. This helps the player feel closer to the stimulus. A drum machine or metronome was connected as the source. This allowed the musician to practise playing m Although the embodiment described is a guitar, the invention could be applied to any instrument having strings, such as a piano or a violin. The additional loudspeaker (31) and the cable (33) are not essential and may be omitted for some applications.

Claims: CLAIMS 1. A musical instrument (1) comprising at least one string (7) that can be vibrated to produce sound; a transducer (21) for picking up electrical signals from the instrument; a processor (23) for processing the electrical signal; a soundboard (3) ; and an exciter (29) on the soundboard (3) for exciting the soundboard (3) with the processed electrical signal to produce an acoustic output. 2. A musical instrument according to claim 1 wherein the processor (23) provides a changing frequency shift to the signal picked up by the transducer (21) . 3. A loudspeaker according to claim 1 or 2 wherein the transducer (21) for picking up electrical signals is also used as the exciter (29) . 4. A musical instrument according to claim 1 or 2 wherein the transducer (21) is located next to the at least one string (7) to pick up the vibration of the string. 5. A musical instrument according to claim 4 wherein the at least one string (7) is made of ferromagnetic material and the transducer (23) is a magnetic pickup. 6. A musical instrument (1) comprising a soundboard (3), at least one string (7) , the string being capable of being vibrated mechanically by a player of the musical instrument , a mechanical coupling (9) mechanically coupling the at least one string (7) to the soundboard (3) , so that vibrations of the string are coupled to the soundboard to produce an acoustic output, an input signal connector (35) for inputting an input signal to the musical instrument, and an exciter (29) mounted on the soundboard (3) and coupled to the input signal connector (35) to excite the soundboard (3) to produce sound corresponding to a signal applied to the input signal connector (35) , so that the soundboard (3) can be excited simultaneously by the exciter (29) and the vibrations of the string (7) to produce a combined output sound signal. 7. A musical instrument (1) according to any preceding claim which is a string instrument wherein the at least one string (7) can be plucked or bowed to produce sound . 8. A musical instrument according to any preceding claim wherein the processor (23) is a microprocessor capable of producing a reverberation effect. 9. A musical instrument according to any preceding claim further comprising a control panel (27) connected to the processor (23) for controlling the sound produced by the instrument . 10. A musical instrument according to any preceding claim further comprising an electrical output connector (35) for outputting a sound signal so that the sound of the instrument may be replayed on conventional loudspeakers. 11. A loudspeaker according to any preceding claims wherein the body (3) of the instrument forms the soundboard. 12. A loudspeaker according to any preceding claim further comprising an electrical input connector (35) for connection to a cable (33) for inputting a sound signal that may be fed to the exciter (27) to produce a corresponding acoustic output . 13. A musical instrument according to any preceding claim further comprising a loudspeaker (31) mounted on the instrument and connected to the processor (23) .

Inventors: COLLOMS MARTIN, WARRINER MARK, COLLOMS, MARTIN, WARRINER, MARK
Applicants: COLLOMS MARTIN, NEW TRANSDUCERS LTD, WARRINER MARK, COLLOMS, MARTIN, NEW TRANSDUCERS LIMITED, WARRINER, MARK
Application year: 2000
Main classification: G10H3
IPC codes: G10H1, G10H3