Patent Publication Number: US-10777181-B2

Title: Modulated electromagnetic musical system and associated methods

Description:
RELATED APPLICATIONS 
     This application is a 35 U.S.C. § 371 filing of International Application No. PCT/US2017/041403, filed Jul. 10, 2017, which claims priority to U.S. Patent Application Ser. No. 62/360,445, titled “Electromagnetic ally Augmented Musical Instrument Methods and Systems,” filed Jul. 10, 2016, each of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Musical instruments, such as the strings, horns, brass, woodwinds, and percussion of the modern orchestra and the multitude of other non-western instruments from around the world have been known for centuries. Conventional musical instrument development has attempted to create new behaviors and new sounds, from both a purely acoustic and electroacoustic perspective. For example, modern guitars have developed significantly since the early invention of the first guitar. Similarly, the invention of the synthesized drum or drum machine provided an entirely new palette of sonic options. 
     In an electroacoustic musical instrument, a substantially acoustic signal is converted to an electric representation of that signal and then manipulated by electronic devices. An electro-acoustic example would be an electric guitar which has the ability to encode the acoustic vibrations of a string into an electrical signal via an electromagnetic pickup. The resultant electrical signal may then be routed through any number of electrical devices that purposely affect the electrical signal to create new sounds. 
     One such new sound, for example, would be the tremolo sound effect, which is now a common musical effect. The acoustic tremolo effect is a flutter-like effect that alters the frequency of the affected tone by some arbitrary modulation, which is typically produced by mechanical or electromechanical induction of a tremolo effect via acoustic amplitude frequency or phase modulation. The acoustic tremolo sound effect can be achieved by applying a mechanically induced modulation with first the Hammond Tone Cabinet (D-20) and later the Leslie Speaker (see U.S. Pat. No. 2,450,139 by Hartsough, and U.S. Pat. No. 3,014,192 by Leslie). The acoustic tremolo effect has some limitations, in that; the frequency range of the modulator is limited to low frequency oscillation below 100 Hz. Other well-known analog circuit effects can be produced through a combination of transistors, capacitors, amplifiers, inductors, and other suitable electrical and/or electronic devices. 
     Another example of an electro-acoustic development is a sound synthesizer or an electronic musical instrument that generates electric signals that are converted to sound through instrument amplifiers and loudspeakers or headphones. U.S. Pat. No. 4,018,121, by Chowning (hereinafter “Chowning”) discloses frequency modulation (FM) for musical sound synthesis. The popularity of the sound synthesizers in popular music resulted in the development of digital modular synthesizers and digital software synthesizers, which resulted in a move away from analog electric musical instruments. In some embodiments, the input signals are generated by a computer system, based on mathematical and physical models of known acoustic systems or methods of digital signal processing (see U.S. Pat. No. 6,049,034 by Cook). 
     An example of an acoustic instrument electromagnetic (EM) augmentation is the control for musical instrument sustainers, or E-Bow, (see U.S. Pat. No. 6,034,316 by Hoover). This device amplifies feedback with an electromagnet to vibrate ferromagnetic strings and sustain the tones continuously. 
     An example of an acoustic instrument electromagnetic (EM) incorporated directly into the design of an electric instrument is the Rhodes piano (see U.S. Pat. No. 3,418,417A by Rhodes and DE2,264,786A1 by Rhodes) This device utilizes single-tine tuning forks to generate tones, which are picked up by a transducer that converts the vibrations into electrical signals, and then connected to an amplifier and a speaker and amplified 
     Another example of an acoustic instrument that has been augmented with electronics is a magnetic resonator piano as described by McPherson &amp; Kim [Augmenting the Acoustic Piano with Electromagnetic String Actuation and Continuous Key Position Sensing, 2010. In  NIME  (pp. 217-222)] or the Rhodes piano, which uses a single-tine fork driven by an electromagnet. Other examples include the overtone fiddle and the feedback resonance guitar (see [Advancements in actuated musical instruments. Organised Sound, 16(2), p 154-165 by Overholt, Berdahl, and Hamilton, 2011]). There currently lacks technology that allows the flexibility of modulation found on sound synthesizers on acoustic or augmented acoustic instruments. This invention bridges this gap between electronic and acoustic methods of synthesizing sound through intermodulation and frequency modulation. 
     An acoustic modification or augmentation of a sound reproduction system is also possible. U.S. Pat. No. 1,346,491 discloses example acoustic amplification and filtering using a waveguide or horn to increase the loudness and directionality of the sound signal. 
     Chowning&#39;s seminal work drew inspiration from the spurious frequency products found from frequency modulation in radio engineering. Similarly, spurious frequency products called intermodulation products typically warrants mitigation, for instance in speaker design (see U.S. Pat. No. 3,327,043A, by Martin). Recently intermodulation has been utilized in the field of Dynamic Atomic Force Microscopy (see U.S. Pat. No. 8,849,611 by Haviland et al.). Expanding frequency content rather than reducing it, rich frequency content can be produced. 
     BRIEF SUMMARY OF THE INVENTION 
     By applying a similar construction as Haviland&#39;s cantilever AFM technique and analogous physical systems, modulation products from different modulation techniques may be leveraged for the synthesis of acoustic sound. 
     Systems and methods produce modulation in electromagnetic (EM) musical systems. In one embodiment, a modulated EM musical system (also referred to as an augmented electromagnetic (EM) musical instrument system) is an augmented, or modified, musical instrument. In another embodiment, the modulated EM musical system is a sound reproduction system. The modulated EM musical system includes at least four key elements: (a) an acoustic carrier signal source, (b) a modulation signal source, (c) a linkage element that exhibits nonlinear behavior such as frequency mixing when driven, and (d) an acoustic output whose coupled interaction with a nonlinear interface produces nonlinear acoustic synthesis. Modulation types may include amplitude modulation, intermodulation, and frequency modulation. 
     Intermodulation products appear when two signals are put through a nonlinear interface, and produces high order sum-and-difference of the signal frequency&#39;s harmonics. This produces rich frequency content that may be used to synthesize sound. Similarly, manipulation of the modulated EM musical system to produce frequency modulation may also produce rich frequency content. 
     A harmonic oscillator is a simple signal source, where an acoustic carrier harmonic oscillator may be a physical oscillator such as a tuning fork or string actuated through the Lorentz force, such as via electromagnets. 
     In one embodiment, a modulated EM musical system includes a cantilever with a pointed tip and two EM actuators, such as a transducer, attached to its base. The tip of the cantilever rests lightly on a soundboard material or a drum membrane, and the height may be adjusted from the base of the cantilever. A carrier signal in audible range is driven through one of the transducers and transformed into motion at the cantilever tip. The second transducer modulates this signal by dampening the tip&#39;s motion. This is a similar technique used the field of Dynamic Amplitude Modulation AFM at a much smaller scale for microscopy. 
     In one embodiment, a modulated AM musical system uses an electromechanical linear actuator with a rubber, foam, or leather covered rigid member to attenuate high frequency energy in a time-varying manner without drastically changing the pitch or frequency of the tone (which occurs if the sound is fully stopped on a horn or other brass instrument). The carrier signal is produced either by human actuation (e.g. blowing) or by mechanical and/or electromechanical means, such as one or more of bellows (e.g., an organ), an actuator, and so on. 
     In one embodiment, an modulated AM musical system includes: an acoustic carrier harmonic oscillator; an EM actuator configured to interact with the acoustic carrier harmonic oscillator at a first frequency to produce a carrier signal having a carrier signal frequency; a dampener assembly positioned a first distance from the acoustic carrier harmonic oscillator and configured to modulate an amplitude of the carrier signal by interacting with a limited cross section of the acoustic carrier harmonic oscillator at a second frequency to generate an EM output signal associated with a produced sound. The acoustic carrier harmonic oscillator is one of a metallic string, metal bar, asymmetric tuning fork, and non-pitched percussion. 
     In one embodiment, the dampener excitation device is a second EM actuator. In another embodiment, the dampener excitation device is a voice coil motor having a rigid member, wherein the first distance is zero and the rigid member engages the limited cross section of the acoustic carrier harmonic oscillator. 
     In one embodiment, the dampener assembly further includes a damping material in contact with the acoustic carrier harmonic oscillator and made from at least one of cloth, rubber, and synthetic elastic material. In another embodiment, the EM actuator further includes a damping material in contact with the limited cross section of the acoustic carrier harmonic oscillator and made from at least one of cloth, wool, leather, foam, rubber, and synthetic elastic material. The dampener assembly may interact with the limited cross section of the acoustic carrier harmonic oscillator in one or multiple planes. 
     In another embodiment, the modulated EM musical system further includes a frame structure to isolate the dampening assembly the first distance from the acoustic carrier harmonic oscillator. Another embodiment the modulated EM musical system further includes a spring suspension mechanism having at least two legs and a spring, wherein the spring engages the acoustic carrier harmonic oscillator on a first end thereof and the spring suspension mechanism is situated at a second end of the acoustic carrier harmonic oscillator. The spring suspension mechanism may engage the soundboard resonator. The spring suspension mechanism may further include at least two isolation pads that engage a bottom surface on at least one of the legs. In one embodiment, the modulated EM musical system further includes an interface coupled to the EM actuator that is driven by software configured to control the first frequency. 
     In another embodiment, the soundboard resonator is coupled to the EM output receiver and configured to modify the received EM output signal for audio effects and amplification. In a further embodiment, the EM output receiver is coupled to an audio input module that is configured to: generate a feedback signal in response to the received EM output signal, and transmit the generated feedback signal to the audio input module, to then generate an audio input signal in response to the received feedback signal. 
     In another embodiment, a method modulates an acoustically generated carrier signal. An EM musical instrument has an actuator, an acoustic harmonic oscillator, and a dampening apparatus. An electromagnetic signal is applied to an acoustic carrier harmonic oscillator by means of the actuator to generate a carrier signal frequency and time varying contact is applied from the dampening apparatus to a limited cross section of the acoustic carrier harmonic oscillator to produce amplitude modulation of an acoustic sound. 
     In another embodiment, a modulated electromagnetic (EM) musical system includes an acoustic carrier signal source for generating an acoustic carrier signal, an EM actuator configured to generate an acoustic modulator signal, a linkage element that exhibits nonlinear behavior when mixing the acoustic carrier signal and the acoustic modulator signal, and an acoustic output coupled with the linkage element to generate acoustic modulation. 
     In another embodiment, a method modulates an acoustic carrier signal using a tipped-cantilever linkage element physically coupled to a source of the acoustic carrier signal. An EM actuator is controlled to impart an acoustic modulator signal to the tipped-cantilever linkage element, and a tip of the tipped-cantilever linkage element causes a nonlinear interaction with an acoustic output to modulate the acoustic carrier signal. 
     In another embodiment, an electromagnetic (EM) musical instrument has acoustic signal modulation and includes an harmonic oscillator for generating an acoustic carrier signal at an approximate harmonic frequency, a dampener positioned a first distance from the EM driven harmonic oscillator, an EM driven transducer for generating a modulation signal to control the dampener to modulate the acoustic carrier signal, and a linkage element coupling the EM driven transducer to the dampener to apply time varying contact of the dampener to the EM driven harmonic oscillator to modulate the acoustic carrier signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an electromagnetically augmented musical instrument system, in an embodiment. 
         FIG. 1B  is an enlarged top view of the electromagnetically augmented musical instrument system of  FIG. 1A . 
         FIG. 2  is a front view of an electromagnetically augmented musical instrument system with portions of a dampening system housing removed, in an embodiment. 
         FIG. 3  is a top perspective view of an electromagnetically augmented musical instrument system, in an embodiment. 
         FIG. 4  is a flowchart illustrating one example method of intermodulation, amplitude modulation, and/or frequency modulation of an electromagnetically augmented musical instrument, in an embodiment. 
         FIG. 5  is a perspective view of an electromagnetically augmented musical instrument system, in an embodiment. 
         FIG. 6  is a table showing example third-order transfer function expansion, in an embodiment. 
         FIG. 7  is a perspective view of one example cantilever based modulated EM musical system, in an embodiment. 
         FIG. 8  is a perspective view of one example string based modulated EM musical system, in an embodiment. 
         FIG. 9  is a perspective view of one example multiple string based modulated EM musical system, in an embodiment. 
         FIG. 10  is a flowchart illustrating one example method of intermodulation, amplitude modulation, and/or frequency modulation of a modulated EM musical system, in an embodiment. 
         FIG. 11  is a functional block diagram illustrating one example cantilever based modulated EM musical system, in an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Signal modulation is the process of combining two signals to form a third signal containing desired properties of both signals. For example, intermodulation [amplitude modulation] is a form of signal modulation that corresponds to a multiplication in the time domain or convolution in the frequency domain of carrier and modulator signals. The modulation of these two signals produces a continuous range of sidebands that are linear combinations of harmonics present in the carrier signal. In amplitude modulation, the amplitude or “strength” of the carrier oscillations is varied. In the frequency domain, amplitude modulation produces a signal with power concentrated at the carrier signal frequency and two adjacent sidebands. Each sideband is equal in bandwidth to that of the modulating signal, and is a mirror image of the other sideband. 
     Embodiments described herein produce signal modulation in EM musical systems. A polynomial transfer function may describe the frequency content from modulation given an input signal S in  and output signal S out . For example, the transfer function may be written as: 
     
       
         
           
             
               
                 
                   
                     
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                       out 
                     
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                           S 
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                           S 
                           in 
                           2 
                         
                       
                       + 
                       
                         
                           K 
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                           S 
                           in 
                           3 
                         
                       
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                           K 
                           4 
                         
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                           S 
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                         … 
                       
                     
                   
                   = 
                   
                     
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                         K 
                         i 
                       
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                         S 
                         in 
                         i 
                       
                     
                   
                 
               
               
                 
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     In the scenario of two tone intermodulation, the input signal is a sum of the acoustic carrier signal and the acoustic modulating signal. For example, two sinusoids may be given by:
 
 S   in   *A  cos ω a   t+B  cos ω b   t  
 
     The order of intermodulation is given by how many terms the transfer function has. A third-order intermodulation would have the following output signal:
 
 S   out   ˜K   1 ( A  cos ω a   t+B  cos ω b   t )+ K   2 ( A  cos ω a   t+B  cos ω b   t ) 2   +K   3 ( A  cos ω a   t+B  cos ω b   t ) 3  
 
     The expansion of this produces 12 harmonic and intermodulation products controllable through input signal strength A and B.  FIG. 6  shows a table  600  illustrating example third-order transfer function expansion. 
     Synthesis up to 15th-order intermodulation has been observed, and coupled with frequency modulation, the output signal may be further controlled. 
       FIG. 1A  is a perspective view of an electromagnetically augmented musical instrument system  1 , in an embodiment.  FIG. 1B  is an enlarged top view of the electromagnetically augmented musical instrument system  1  of  FIG. 1A .  FIGS. 1A and 1B  may be collectively referred to as  FIG. 1  herein. The system  1  includes an actuator  10 , an acoustic carrier harmonic oscillator  12 , a dampener  18 , dampener material  20 , a limited cross section of the acoustic carrier harmonic oscillator  22 , a distance  24  between the dampener  18  and the acoustic carrier harmonic oscillator  12 , a distance  26  between the actuator  10  and the acoustic carrier harmonic oscillator, a spring suspension subsystem  28 , a soundboard or soundboard resonator  30 , isolation pads  32 , a structural frame  35 . It is foreseen that the electromagnetically augmented musical instrument system  1  may further include amplification circuitry (not shown), as well as a transducer (not shown), such as a microphone or speaker. The soundboard  30  forms an acoustic output. 
     In the illustrated example of  FIG. 1 , the actuator  10  is a cylindrical solenoid electromagnet, which may include multiple turns of wire around a central core made of iron, steel, or other ferromagnetic material, one such example is a Magnet Sensor Systems Series E-77-82 having a pull force of 14.4 lbs. at 8.75 Watts on a 0.125 in of cold rolled steel. The actuator  10  is connected with the structure frame  35  and situated a distance  26  away from the acoustic body  12  ( FIG. 1 b   ). 
     The actuator  10  exerts a time-varying force on an acoustic body or acoustic carrier harmonic oscillator  12 , such as an asymmetric tuning fork, metal bars, strings such as guitar strings, violin strings, piano strings, a snare drum, a pipe organ, a marimba bar, drum head, non-pitched percussion, etc. The acoustic carrier harmonic oscillator  12  in the illustrated example is a steel (semi ferrous) tuning fork. 
     In certain embodiments, where the acoustic body  12  is non-ferrous or slightly ferrous, a magnet (not shown) may be attached to acoustic carrier harmonic oscillator  12  so that the non-ferrous acoustic body  12  may be activated through the attached magnet (not shown). The actuator  10  may be offset from the magnet (not shown) rather than orthogonal to. 
     In certain embodiments, the actuator  10  is a Lorentz Force actuator. The size and geometric cross section may be different than what is illustrated. The actuator may be larger or smaller in dimension and may be a different geometric shape, such as rectangular, square, etc. In certain embodiments, actuator  10  may be a first actuator of a series of actuators (not shown) configured in series, parallel, or circumferential. The actuator  10  may be driven by software or hardware components or some combination thereof. The actuator  10  may be a signal corrected live input. 
     The actuator  10  drives the acoustic carrier harmonic oscillator  12  at a frequency, i.e. half or quarter of a natural frequency of the acoustic carrier harmonic oscillator  12 , see FIG. 2 in Appendix A of U.S. Patent Application Ser. No. 62/360,445 (Appendix A provides, for disclosure purposes, a journal paper entitled “Electromagnetically Actuated Acoustic Amplitude Modulation Synthesis”). The electromagnetic force generated by the actuator  10  produces or induces vibrations in the acoustic carrier harmonic oscillator  12 , thereby creating a sound output for the instrument system  1  without external audio effects and without delay, as the electromagnetic does not need a warm up delay. The actuator  10  produces an acoustic carrier signal with the symmetric tine  36  movement of the fork generating an efficient, almost perfectly sinusoidal motion in a horizontal direction (single degree of freedom) of a stem  34  or lower portion of the fork. The vibration creating an acoustic output sound. If the actuator  10  drives the tines or prongs  36  of the steel tuning fork  12  at half or one-fourth its natural frequency, this configuration produces at least one salient carrier signal at a natural frequency or some multiple of the natural frequency. 
     If one were to strike a tuning fork  12  or pluck string (see for example  FIG. 8 ), its sound gradually decreases in volume with time, which is usually represented by a change damping value. This corresponds to the transient dissipation of energy after an initial force. The driving frequency of the actuator  10  is held constant to produce a consistent carrier signal at least one of the natural frequencies, as there may be more than one frequency in which resonance is reached. 
     To manipulate the sound output, the dampener  18  modulates the amplitude of the carrier signal of the acoustic body  12  (e.g. tuning fork  12 ). The modulation produces sidebands, which in turn create unique and non-linear sound outputs and effects. The dampener  18 , in the illustrated embodiment of  FIG. 1 , is a time varying dampener (TVD), in that, it is a second EM actuator having a second driving frequency. Displacement of the fork tines  36  determines the amplitude of the periodic carrier signal, and ultimately the output sound, thus modulating the displacement of the forks prongs  36  through dampening produces an intermodulation, amplitude modulation, and/or frequency modulation of the carrier signal. The second EM actuator or dampener  18  applies force or electromagnetic pull to the fixed stem  34  and causes acoustic body  12  to pivot slightly. When the acoustic body  12  pivots, the actuator  10  is no longer at the distance  26  away from a prong  36 , i.e., 2 mm, and the acoustic body  12  makes contact with the actuator  10  at a small cross section  22  of the prong  36 . The angle of adjustment (not shown) is small and contact area  22  is small, but contact between the tuning fork tine  12  and the actuator  10  produces the amplitude modulating TVD effect. The effect corresponds to a non-sinusoidal, periodic modulation signal that is controlled by the frequency or pulse length of the dampener  18 . Since the constant drive frequency from the carrier electromagnet actuator  10  continues to excite the tines  36 , the natural frequency of the tuning fork  12  remains the same even through the small contact with the actuator  10 . 
     The dampening effect alters the loudness of the sound to produce harmonics called sidebands, which are a byproduct of attenuation of the amplitude (or loudness) of the carrier signals. The dampening effect creates an altered sound output or timbre of the augmented musical instrument system  1 . The dampening system  18  allows for a tremolo effect at higher frequencies, i.e. above 100 Hz. It is foreseen that the dampening frequency my further include delays, stops, or timed pulses. It is also foreseen that the dampener  18  may include more than one dampener either along one plane or multiple planes about the acoustic body  12 . The actuator  10  and dampening system  18  are illustrated along one plane and thereby affect one single degree of freedom with respect to the tuning fork  12 , but it is foreseen that several actuators (not shown) may generate complex timbre using multiple locations across several degrees of freedom. 
     In the illustrated example, a dampening material  22  covers or substantially covers an end  27  of the actuator  10 . The dampening material  22  is purposed to interact with the contact area  22 . The actuator  10  still maintains a distance  26  away from the prong  36  of the tuning fork  12  with the dampening material  38  covering the end  27 . The dampening material  22  may be made of cloth, wool, foam, leather, synthetic plastic, rubber, and may further include adhesive material (not shown). 
     A spring suspension system  28  includes at least one spring  40  and a base or amplifier interface  42 , and steel end blocks  44 . The base  42  has at least two legs  43  or is T-shaped. The spring suspension system  28  further includes an aperture or hole (not shown) for which the acoustic body  12  is situated within. In the illustrated embodiment, the springs  40  engage the stem  34  of the tuning fork  12  and are attached at opposed ends  46  to the steel end blocks  44 . Two end-blocks  44  control the tension of the springs  40  to restore or force the stem  34  to return to the mass&#39;s equilibrium position. In the illustrated example, the equilibrium position is upright or vertical. 
     The sound output is transferred from the prongs  36  of the tuning fork to the stem  34  and finally to the acoustic soundboard  30 . The base  42  acoustically transduces the output sound from the stem  34  into the soundboard or acoustic amplifier  30 . The illustrated T-frame base  42  is designed to separate the structure holding the electromagnetic actuators  10 ,  18  from the tuning fork  12  and act as a stabilization mechanism  28 . The T-frame base  42  and springs  40  may be made from plastic, metal, or metal alloys. 
     The loss or decreased signal bleed caused by vibration and other noise generated by the EM actuators  10 ,  18 . Additional non-active components may decouple the force generating noise from the desired output signals and acoustically amplify the signals. Sound isolation pads  32  further reduce propagation of noise through the suspension system  28 . To amplify the desired signals, a thin soundboard or acoustic resonator  30  consistent with surfaces commonly used to amplify tuning forks  12  is connected with the suspension system  28 . A soft foam structure (not shown) is foreseen to be located below the soundboard  30 . 
     A second embodiment is shown in  FIG. 2 , therein illustrated an electromagnetically augmented musical instrument system  100  in accordance with the present invention. The system  100  includes an actuator  110 , an acoustic carrier harmonic oscillator  112 , a dampening system  118 , dampener material  120 , a limited cross section of the acoustic carrier harmonic oscillator  122 , a distance (not shown) between the dampener  18  and the acoustic carrier harmonic oscillator  112 , a distance  126  between the actuator  10  and the acoustic carrier harmonic oscillator, an amplifier interface  128 , a soundboard or amplifier resonator  130 , isolation pads  132 , and a structural frame  135 . It is foreseen that the electromagnetically augmented musical instrument system  100  may further include amplification circuitry (not shown), as well as a transducer (not shown), such as a microphone or speaker. 
     In the illustrated example of  FIG. 2 , the actuator  110  is substantially similar to the actuator  10 . The actuator  110  is connected with a flexible structural frame  135 . The actuator  110  is positioned a distance  126  away from the acoustic body  112 . The acoustic carrier harmonic oscillator  112  in the illustrated example is a steel (semi ferrous) tuning fork and is substantially similar to the acoustic body  12 . 
     The dampener assembly  118  in the illustrated embodiment is a time varying dampener (TVD), in that, the dampening system  118  includes an electric motor  119 , such as a linear DC motor, voice coil motors (VCM) or voice coil actuators (VCA). The motor  119  having a second driving frequency, i.e. between 0.01 Hz to 15 kHz in which it may operate. The peak performance of the augment instrument  100  is when the dampener assembly  118  is driven between twice the carrier signal frequency minus 200 Hz. The motor  119  uses a stationary coil (not shown) to vibrate a magnetized piece of metal, iron, reed, rigid membrane, or armature  121 . The armature  121  is positioned in a plane orthogonal to a plane in which the actuator  110  is situated. 
     Displacement of the fork tines  136  determines the amplitude of the periodic carrier signal, and ultimately the output sound, thus modulating the displacement of the forks prongs  136  through dampening from the dampening system  118  produces an intermodulation, amplitude modulation, and/or frequency modulation of the carrier signal of the tuning fork  112 . The motor  118  vibrates the rigid membrane  121 , such that, the rigid membrane  121  makes contact with at least one of the fork prong  136  or to the fixed stem  134  and thereby, causing modulation of the amplitude of the carrier signal of the acoustic body  112 . 
     It is envisioned that the distance  124  from the rigid membrane  121  from the acoustic body  12  is a distance, but for practical reasons that distance may approximate zero. The vibration of the armature  121  and contact area  122  may be small, but this small contact between the tuning fork tine  136  and the armature  121  produces the amplitude modulator actuated TVD effect. The effect corresponds to a non-sinusoidal, periodic modulation signal that is controlled by the frequency or pulse length of the dampener motor  119 . Since the constant drive frequency from the carrier electromagnet actuator  110  continues to excite the tines  136 , the natural frequency of the tuning fork  112  remains the same even with the small contact from the armature  121 . This is not true for augmented non-actuated acoustic musical instruments, as will be further discussed below. 
     The dampening alters the loudness of the sound to produce sidebands with each contact creating an altered sound output or timbre. The dampening system  118  allows for a tremolo affect at higher frequencies. It is foreseen that the dampening frequency my further include delays, stops, or timed pulses. It is also foreseen that the dampener  118  may include more than one dampener either along one plane or multiple planes. 
     In the illustrated example, the dampening system  118  includes a dampening material  122  covering or substantially covering an end  127  of the armature  121 . The dampening material  122  is purposed to interact with the contact area  122  of the acoustic body  12 , shown in  FIG. 2  at the stem  134 . The dampening material  122  may be made of cloth, wool, foam, synthetic plastic, rubber, and may further include adhesive material (not shown). 
     The amplification interface  128  includes a base  142  has at least two legs  143  or is T-shaped, as illustrated. The amplifier interface  28  further includes an aperture or hole (not shown) for which the acoustic body  112  is situated within. The illustrated T-Frame base  42  is designed to separate the structure  135  holding the electromagnetic actuators  110  from the tuning fork  112  and soundboard  130 . The T-frame may be made from plastic, metal, or metal alloys or combination thereof. 
     The sound output is transferred from the prongs  136  of the tuning fork to the stem  134  then to the base  142  which is connected to an acoustic soundboard  130 . The base  142  acoustically transduces the output sound from the stem  34  into the soundboard or acoustic amplifier  130 . The acoustic soundboard  130  is substantially similar to the soundboard  30 , as explained above. 
     Sound isolation pads  132  further reduce propagation of noise through the interface  28 . The sound isolation pads  132  are located on a bottom surface (not shown) of the interface base  142 . A soft foam structure  140  is located below the soundboard  130 . 
     A third embodiment of the present invention is shown in  FIG. 3 , therein illustrated an electromagnetically augmented musical instrument system  200  in accordance with the present invention. The system  200  includes an instrument bridge  201 , a series of acoustic carrier harmonic oscillators  212 , a dampening subassembly  218 , a spring suspension system  228 , and an instrument body  235 . It is foreseen that the electromagnetically augmented musical instrument system  200  may further include amplification circuitry (not shown), as well as a transducer (not shown), such as a microphone, sensor, or speaker. 
     In the illustrated example of  FIG. 3 , the series of acoustic carrier harmonic oscillators  212  are illustrated as six individual strings  213  terminated at the bridge  201 , each string  213  is actuated at its natural frequency by a user to generate force by bowing, plucking, striking, rubbing, or blowing and is not electromagnetically activated. It is foreseen that the musical instrument system could include more or less individual strings  213 . 
     The dampener assembly  118  in the illustrated embodiment, is series of time varying dampeners (TVD), in that, it is a series of electric motors  219 , such as a linear DC motor, voice coil motors (VCM) or voice coil actuators (VCA) each having a driving frequency within standard operating ranges, which include the audible frequency range. Each motor  219  being capable of being driving at the same frequency at the same time or different. Each of the motors  219  is housed in a sound isolating bridge structure or housing  202  that is situated above the bridge  201 . Each of the motors  219  use a stationary coil (not shown) to vibrate a magnetized piece of metal, iron, reed, rigid membrane, or armature  221 . Each of the armatures  221  are positioned in a plane orthogonal to a plane in which the strings  213  are activated. 
     Displacement of at least one string  213  determines the amplitude of the periodic carrier signal, and ultimately the output sound, thus modulating the displacement of the string  213  through damping from the dampening system  218  produces an intermodulation, amplitude modulation, and/or frequency modulation for each string that is activated or user dependent, meaning it is foreseen that at least one dampener motor  219  may not become activated when the string  213  is actuated. It is envisioned that at least one of the motors  218  vibrate the respective rigid membrane  221 , such that, the rigid member  221  makes contact with the respective string  213  and causes modulation of the amplitude of the carrier signal of the strings  213 . 
     It is envisioned that the distance from the rigid membrane  221  from the respective strings  213  is an equal distance  224 , which may approximate zero. It is foreseen that at least one motor  219 , the distance  224  could be different than the others in the series  218 . The vibration of the armature  221  causes the armature  221  to make contact with a small contact area  222  on the string, which in turn produces the amplitude modulator actuated TVD effect. This corresponds to a non-sinusoidal, periodic modulation signal that is controlled by the drive frequency or pulse length of the dampener motor  219 . As discussed above, it is foreseen that at least one motor  219  in the series of dampeners  218  may be off. 
     The dampening effect of each motor  219  alters the sound and the sidebands of the carrier signal to create an altered sound output or timbre for each individual string  213 . The dampening system  218  allows for a tremolo effect at higher frequencies. It is foreseen that the dampening frequency my further include delays, stops, or timed pulses. It is also foreseen that the dampener  218  may include more than one dampener per string  213  either along one plane, multiple planes, or circumferential. 
     In the illustrated example, the dampening system  218  includes a dampening material  222  covering or substantially covering an end  127  of each of the armatures  221 . The dampening material  222  is purposed to interact with a small contact area  222  of the string  213 . The dampening material  222  may be made of cloth, wool, foam, synthetic plastic, rubber, and may further include adhesive material (not shown). 
     An amplifier interface  228  includes a base  242 , which has at least two legs  243  or is T-shaped, as illustrated. The amplifier interface  228  is located below a series of saddles  203  that hold the strings  213  at a height above the instrument frame or wooden soundboard  235 . The vibrating wooden soundboard  235  creates a richer tone than vibrating stings alone. The vibrating wooden soundboard  235  forms an acoustic output. A vibrating acoustic soundboard  235  is typically louder than the strings  213  alone. The characteristic sound of an acoustic stringed instrument is predominantly created by the amplification made by the soundboard  235 , not the strings  213  themselves. The amplifier interface  228  further includes an aperture or hole (not shown) for which at least one string  213  is situated within. The T-frame may be made from plastic, metal, or metal alloys or some combination thereof. It is foreseen that sound isolation pads (not shown) may be situated below the base  242  to further reduce propagation of noise through the suspension system  228 . 
     It is foreseen that the musical instrument system  1 ,  100 ,  200  may further include a microphone, such as Earthworks QTC50 omnidirectional microphone or a Shure SM58 situated a distance from the soundboard, i.e. 20 mm. It is foreseen that musical instrument systems  1 ,  100 ,  200  may further include amplification effects once sampled through the microphone. It is foreseen that the electromagnetically augmented musical instrument systems  1 ,  100 ,  200  may create a self-feedback using a pickup, sonic transducer, or via acoustic feedback to modify the signal through a subtractive or additive synthesis. It is foreseen that the present invention could further include sensors, such as Piezo sensors to sense vibrations of the acoustic body  12 . 
       FIG. 4  is a flowchart illustrating one example method  400  of intermodulation, amplitude modulation, and/or frequency modulation of an electromagnetically augmented musical instrument. 
     At block  401 , a carrier signal and frequency is generated. This block may be performed by an actuator, for example the actuator  10  of  FIG. 1 , or by physical force generated by bowing, plucking, striking, rubbing, or blowing, or manipulation of an acoustic carrier harmonic oscillator, such as the acoustic body  12  of  FIG. 1 . The carrier signal being a sound. 
     At block  403 , a dampener is provided that is configured to make physical contact with a small contact area  22  of the acoustic carrier harmonic oscillator  12 . This block may be performed by a second actuator, for example the dampener  18  of  FIG. 1  or the dampener  118  of  FIG. 2  as described above. The dampener manipulates the carrier signal amplitude or strength through modulation, thereby outputting a manipulated audio acoustic sound. This block may include dampener frequency adjusts with delay components or pulses. 
     At block  405 , a suspension system may stabilize the acoustic carrier harmonic oscillator back to its initial position, thereby returning the carrier signal back to the original amplitude. At this block, if there are no springs, then the suspension system may also act as an amplifier interface that connects the acoustic body  12  to the soundboard  30 . 
     At block  407 , the output audio acoustic sound is amplified. This block may be performed a soundboard, for example the soundboard  30  of  FIG. 1 . 
     At block  409 , the output audio acoustic sound is observed. This may also be observed by electronics such as a transducer, sensors, amplifier, or receiver. 
       FIG. 5  is a perspective view of an electromagnetically augmented musical instrument system  500 , wherein a wind, brass, and organ instrument may be altered. The system  500  includes an, an acoustic carrier harmonic oscillator  512 , a dampener assembly  518 , dampener material  520 , a limited cross section of the acoustic carrier harmonic oscillator  522 , a distance  524  between the dampener assembly  518  and the acoustic carrier harmonic oscillator  522 , a structural frame  535 . In certain embodiment, the electromagnetically augmented musical instrument system  500  may further include amplification circuitry (not shown), as well as a transducer (not shown), such as a microphone or speaker. 
     The dampener assembly  518  may be a baffle or membrane set across the opening of a wind instrument and actuated by the EM Actuator. The combination of the membrane and fluid around it acts as the linkage element. The physical medium is air, although propagation in any fluid medium is possible, such as water or other liquids. 
       FIG. 7  is a perspective view of one example cantilever based modulated EM musical system  700 . Modulated EM musical system  700  uses a cantilever  706  with a pointed tip  708  as the linkage element, an acoustic carrier transducer  702  and a modulation transducer  704 . The pointed tip  708  of the cantilever  706  rests lightly on a soundboard  710 . The height of the cantilever  706  and tip  708  may be adjusted from the base of the cantilever. The nonlinear interaction between the tip  708  and the soundboard  710  produces the intermodulation as described above for system  1 . In the example of  FIG. 7 , acoustic carrier transducer  702  is a piezoelectric transducer that forms a carrier signal source that is injected into the cantilever  706 . The modulation transducer  704  is a voice coil that provide an EM modulator signal that is applied to the acoustic carrier transducer  702 . 
     The cantilever  706  is formed as a thin rectangular copper metal that is affixed to the modulation transducer  704 . The motion imparted to the cantilever  706  by the acoustic carrier transducer  702  and the modulation transducer  704  is transferred to the cantilever tip  708  and produces sideband frequency components on the soundboard  710  to form an output signal (e.g., a sound). The nonlinear interaction between the tip  708  and the soundboard  710  generates additional frequency components. The cantilever design produces amplified motion at the tip  708  as compared to motion of the actuators  702  and  704 . The soundboard  710  is a physical medium that amplifies the output signal to produce the sound. The soundboard  710  thereby forms an acoustic output. A foam  712  may be used for sound isolation to mitigate transduction of vibration between the system  700  and a platform the system is placed upon. 
     The cantilever  706  may also be referred to as a linkage element, as described in block  1006  of  FIG. 10 . The modulation transducer  704  is attached beneath the non-tipped end of the cantilever  706 , acting as the acoustic carrier signal source as described in block  1002 . When a signal is injected through the modulation transducer  704 , the cantilever tip  708  oscillates. When driven at a resonant frequency of the cantilever  706 , the oscillation is at maximum. The audible range is sufficiently near the resonance frequency of the cantilever. 
     The acoustic carrier transducer  702  (e.g., a Piezo-transducer) injects the modulation signal source as described in block  1004 . This dampens or exacerbates the motion of the cantilever tip  708 , producing nonlinear motion. 
     The cantilever tip  708  gently rests on the surface of the soundboard  710 . How “gently” may be adjusted by the relative heights of the foam  712 , or, in certain embodiments, may be adjusted with a mechanical screw  714 . The cantilever tip  708 , when in motion, produces a tip-surface nonlinearity that produces additional frequency components known as intermodulation products. The intermodulation products&#39; frequency components take the form of:
 
 k   a ω a   ±k   b ω b  for  k   a   +k   b   ≤N.  
 
     Where ω a  and ω b  are the carrier and modulating frequencies, k a  and k b  are integers, and N is the order of Intermodulation. The weight of these frequency components depend on the material of soundboard  710  and the injected strengths of the carrier and modulator signals. 
     The use of transducers allows direct variation over both the carrier and modulator frequencies and amplitude. Based on variation of material and signal injection, intermodulation is on the order of 10 1 . Frequency modulation may be applied through the injected signal or through a similar process of FM AFM. Not only is this an effective way of modulation, the cantilever  706  has direct application to embodiments of  FIGS. 1, 2, 8, and 9 . 
       FIG. 8  is a perspective view of one example string based modulated EM musical system  800 , in an embodiment. The modulated EM musical system  800  includes an instrument bridge  802  of a string instrument (illustratively shown as part of an acoustic guitar), a carrier signal source  804  consisting of plucked or EM sustained strings, a sound isolating bridge structure housing  806  (similar to sound isolating bridge structure or housing  202  of  FIG. 3 ). The system  800  also includes an EM modulation source  810  that is for example an EM actuator, a cantilever  812 , similar to cantilever  706  of  FIG. 7 , that is supported by a cantilever bridge  808  that transfers energy from the carrier signal source  804  to the cantilever  812 . The cantilever  812  thereby mixes transduced signals from the cantilever bridge  808  and EM modulation source  810  to generate vibration and/or motion at a cantilever tip  814  (e.g., similar to cantilever tip  708  of  FIG. 7 ) where a tip-surface nonlinearity between tip  814  and a soundboard  816  produces additional frequency components within the output signal. The soundboard  816  is a surface of an acoustic guitar or other string instrument, for example. The soundboard  816  thereby forms an acoustic output. 
     The string based modulated EM musical system  800  is analogous to the cantilever based modulated EM musical system  700  of  FIG. 7  with the following key difference in components. The linkage elements (e.g., as referenced in block  1006  of  FIG. 10 ) of the string based modulated EM musical system  800  are formed of a combination of the instrument bridge  802 , the sound isolating bridge structure housing  806 , and the cantilever  812 . Note the form of the sound isolating bridge structure housing  806  depends on the instrument, depicted in  FIG. 8  as an acoustic guitar. The acoustic carrier signal source  804  (as referenced in block  1002 ) is a plucked, EM sustained, or bow sustained string. The modulator signal source (as reference in block  1004 ) is the EM modulation source  810 , which takes an injected signal from an external source or feedback source from a pick-up. With these analogous components, intermodulation as described for  FIG. 7  description is similarly achieved for a stringed musical instrument. 
       FIG. 9  is a perspective view of one example multiple string based modulated EM musical system  900 , in an embodiment. The modulated EM musical system  900  includes an instrument bridge  902  of an acoustic guitar or other string instrument, a carrier signal source  904  consisting of plucked or EM sustained strings, a sound isolating bridge structure housing  906  (similar to sound isolating bridge structure housing  806  of  FIG. 8 ), a cantilever bridge  908  that supports a plurality of cantilevers  912  and transfers energy from the carrier signal source  904  to the cantilevers  912 . The modulated EM musical system  900  also includes a plurality of EM modulation sources  910 , each consisting of at least one EM actuators. The number of EM modulation sources  910  and/or EM actuators may be arbitrary and selected depending on the context or design of the modulated EM musical system  900 . Each cantilever  912  is similar to cantilever  812  of  FIG. 8  and functions to mix the transduced signals from the cantilever bridge  908  and a respective one of the EM modulation sources  910 , resulting in vibration and/or motion at a cantilever tip  914  of the cantilever  910 . There may be an arbitrary number of cantilevers  912  depending on the context or design of the modulated EM musical system  900 . Each cantilever tip  914  is similar to the cantilever tip  814  of  FIG. 8  and functions to mix transduced signals from the cantilever bridge  908  and respective EM modulation source  910  to generate vibration and/or motion at the respective cantilever tip  914  where a tip-surface nonlinearity between tip  914  and a soundboard  916  produces additional frequency components within the output signal. The soundboard  916  is a surface of an acoustic guitar or other string instrument, for example. The soundboard  916  thereby forms an acoustic output. 
     Where  FIG. 8  depicts all signal sources injected through a single bridge and cantilever linkage element (e.g., six strings to one linkage element),  FIG. 9  depicts a configuration with two strings to one linkage element. That is, two strings form the acoustic carrier signal source (as referenced in block  1002 ) for each cantilever  912 . The number of cantilevers  912  may be increased based on the desired ratio of signal sources (e.g., the number of carrier signal sources divided by the number of modulation signal sources). 
       FIG. 10  is a flowchart illustrating one example method  1000  of intermodulation, amplitude modulation, and/or frequency modulation of a modulated EM musical system, in an embodiment. Method  1000  is for example a generalized acoustic modulation synthesis method that may be implemented by any one of electromagnetically augmented musical instrument systems  1 ,  100 , and  500  of  FIGS. 1, 2 and 5 , and modulated EM musical systems  700 ,  800  and  900  of  FIGS. 7, 8 and 9 , respectively. 
     At block  1002 , an acoustic carrier signal is generated. In one example of block  1002 , a string of the modulated EM musical system  800  of  FIG. 8  is plucked. At block  1004 , a modulation signal source(s) makes physical contact with a linkage element. In one example of block  1004 , the EM modulation source  810  imparts a vibration to the cantilever  812 . In block  1006 , the linkage element exhibits controllable nonlinear behavior producing a modulation when driven by the signal sources. In one example of block  1006 , the cantilever tip  814  of the cantilever  812  exhibits controllable nonlinear behavior when driven by the cantilever bridge  808  and EM modulation source  810 . In block  1008 , the linkage element interacts with a physical medium to amplify the modulated signal. In one example of block  1008 , the tip-surface nonlinearity between tip  814  and the soundboard  816  amplifies the modulated signal and produces sound. In block  1010 , the acoustic output is observed. In one example of block  1010 , a listener hears the sound generated by the soundboard  816 . 
       FIG. 11  is a block diagram illustrating one example cantilever based modulated EM musical system  1100 . A signal source may be acoustic or may be generated electromagnetically in many ways. For example, the systems  700  and  800 , shown in  FIGS. 7 and 8 , respectively, may use different types of inputs. The electric inputs may be a signal produced from inserting an 8 mm audio jack, or wired directly, and this signal may be produced from an analog or digital synthesizer, playback from an audio recording, from a live microphone, an input from an electric guitar, or from a pickup attached to a musical instrument. 
     System  1100  is shown with an analog/digital signal generator  1102  and zero, one or more additional inputs  1104  that generate an electrical input. The electric input may be an amplified signal generated on an analog or digital synthesizer, playback from an audio recording, from a live microphone, or from a pickup attached to a musical instrument. The electrical input is input to an analog/digital filter  1106  and the output from the analog/digital filter  1106  is used to drive an EM actuator  1108  that generates a modulation signal source that feeds into a cantilever linkage element  1114 . Cantilever linkage element  1114  may represents one of cantilever  706  of  FIG. 7 , cantilever  812  of  FIG. 8 , and cantilevers  912  of  FIG. 9 . An acoustic signal  1110  from a musical instrument, and zero, one or more additional inputs  1112 , are also input to the cantilever linkage element  1114 , which couples with a physical medium  1116 . 
     As described above with respect to  FIG. 10 , the cantilever linkage element  1114  may include a tip, positioned at the end of a cantilever that exhibits controllable nonlinear behavior when driven by the acoustic signal  1110  and the analog/digital signal generator  1102  to interact with the physical medium  1116 . The physical medium  1116  may in turn couple with an acoustic amplifier  1118  (e.g., one of soundboards  710 ,  816 , and  916  of  FIGS. 7, 8 and 9 , respectively) to output sound. A transducer pickup  1120  may also couple with the physical medium  1116  and generate a feedback signal  1121  that may be input to analog/digital filter  1106 . Output from the transducer pickup  1120  may also drive an audio amplifier  1122  that in turn drives a speaker  1124  to generate an audio output. 
     The outputs of system  1100  may be acoustic sounds, generated directly by the acoustic amplifier  1118  and/or generated by speaker  1124  as driven by the audio amplifier  1122 . 
     Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween. In particular, the following embodiments are specifically contemplated, as well as any combinations of such embodiments that are compatible with one another: 
     (A) A modulated electromagnetic (EM) musical system includes an acoustic carrier signal source for generating an acoustic carrier signal, an EM actuator configured to generate an acoustic modulator signal, a linkage element that exhibits nonlinear behavior when mixing the acoustic carrier signal and the acoustic modulator signal, and an acoustic output coupled with the linkage element to generate acoustic modulation. 
     (B) In the modulated EM musical system denoted as (A), the acoustic modulation including at least one of amplitude modulation, intermodulation, and frequency modulation. 
     (C) Either of the modulated EM musical systems denoted as (A) and (B), further including a second EM actuator that produces a second acoustic modulator signal, and a second linkage element that exhibits nonlinear behavior when mixing the acoustic carrier signal and the second acoustic modulator signal. The second linkage element coupling with the acoustic output to generate second acoustic modulation. 
     (D) In any of the modulated EM musical systems denoted as (A)-(C), the acoustic carrier signal source including at least one of a string, bar, membrane or drum head, symmetric or asymmetric tuning fork, piezoelectric element, and a surface transducer. 
     (E) In any of the modulated EM musical systems denoted as (A)-(D), the acoustic modulator signal source comprises one or more of an EM actuator, transducer, voice-coil actuator, and a shaker. 
     (F) In any of the modulated EM musical systems denoted as (A)-(E), the linkage element including at least one of a cantilever, a t-frame, a baffle, and a bridge, wherein a first distance between the linkage element and the acoustic output is zero. 
     (G) In any of the modulated EM musical systems denoted as (A)-(F), the linkage element assembly further including a material for making continuous or intermittent contact with the acoustic output, the material being selected from the group including metal, wood, cloth, rubber, and synthetic elastic material. 
     (H) In any of the modulated EM musical systems denoted as (A)-(G), the acoustic output is a physical medium that converts and amplifies vibrations into acoustic waves, the acoustic output being selected from the group include solid materials in the form of soundboards, pipes, horns, membranes, planar surfaces, and fluids such as air. 
     (I) In any of the modulated EM musical systems denoted as (A)-(H), the acoustic output including a pickup for converting vibrations into an electrical signal for further processing and/or amplification. 
     (J) In any of the modulated EM musical systems denoted as (A)-(I), the acoustic output is coupled to an audio input module configured to generate a feedback signal in response to the acoustic output, wherein the feedback signal is processed to control the EM actuator to generate the acoustic modulator signal. 
     (K) Any of the modulated EM musical systems denoted as (A)-(J), further including a base structure having vibration absorption materials configured to isolate acoustic output from acoustic carrier signal source, the EM actuator, and the linkage element. 
     (L) A method modulates an acoustic carrier signal using a tipped-cantilever linkage element physically coupled to a source of the acoustic carrier signal. An EM actuator is controlled to impart an acoustic modulator signal to the tipped-cantilever linkage element and a tip of the tipped-cantilever linkage element causes a nonlinear interaction with an acoustic output to modulate the acoustic carrier signal. 
     (M) The method denoted as (L), the modulation being performed through transduction from EM Actuators. 
     (N) In either of the methods denoted as (L) and (M), the modulation resulting from nonlinear motion of a tip of the tipped-cantilever linkage element against the acoustic output. 
     (O) In any of the methods denoted as (L)-(N), the modulation including one or more of amplitude modulation, intermodulation, and frequency modulation. 
     (P) An EM musical instrument having acoustic signal modulation includes an harmonic oscillator for generating an acoustic carrier signal at an approximate harmonic frequency, a dampener positioned a first distance from the EM driven harmonic oscillator, an EM driven transducer for generating a modulation signal to control the dampener to modulate the acoustic carrier signal, and a linkage element coupling the EM driven transducer to the dampener to apply time varying contact of the dampener to the EM driven harmonic oscillator to modulate the acoustic carrier signal. 
     (Q) In the EM musical instrument denoted as (P), the modulation including one or more of amplitude modulation, intermodulation, and frequency modulation. 
     (R) Either of the EM musical instruments denoted as (P) and (Q), further including an EM driver for driving the harmonic oscillator using an electromagnetic signal to generate the acoustic carrier signal.