Electronic musical instrument

An electronic musical apparatus comprising:

• a sound box;
• a fret board coupled to said sound box;
• a plurality of discrete conductive frets disposed on said fret board;
• a plurality of discrete resistive elements coupled to said plurality of discrete conductive frets;
• first means for generating a plurality of tones coupled to said plurality of resistive elements, said first means generating a periodic current;
• a constant amplitude phase shifter having a first node, the periodic current from the first means being coupled to the first node, the phase shifter comprising:
• a current differential amplifier,
• second means coupled between ground and the node for providing a low-resistance path to said periodic current when said periodic current has a first polarity and a high resistance path when said periodic current has a second polarity opposite to said first polarity,
• third means for providing a selective resistance path coupling the input of said amplifier to said node, and
• fourth means coupled between the node and the input of the current differencing amplifier for reflecting the periodic current passing through the second means to the input of the amplifier as a periodic signal which is out-of-phase with the periodic current passing through the second means,
• fifth means for biasing said node to shift said periodic current by a bias current;
• second means having its input coupled to the output of said first means for selectively modifying the frequency spectrum of said plurality of tones generated by said first means and for modifying the waveshape, without substantial alteration of amplitude regardless of the frequency of said plurality of tones, said second means selectively obtaining the output characteristics of a full wave rectifier at a first extreme, obtaining the output characteristics of a voltage follower at a second extreme, and obtaining gradiations between said first and second extremes;
• a source of electrical power;
• and
• conductive means disposed on said fret board and adapted to selectively couple said source of electrical power to at least one of said plurality of discrete conductive frets, whereby musical tones may be audibly generated according to a fixed musical scale in a manner functionally equivalent to conventional stringed instruments.

In a musical instrument, a circuit comprising:

• a plurality of discrete resistive elements, each having a contact node coupled thereto;
• conductive wire means for selectively coupling with at least one of said contact nodes;
• an oscillator coupled to said plurality of discrete resistive elements and said conductive wire means to selectively generate a plurality of periodic electric signals each having a distinct principal frequency and a distinct waveshape definable by a combination of a plurality of sine waves having a frequency spectrum;
• tone enhancement means for selectively altering the frequency spectrum of the plurality of sine waves defining the waveshape for modifying the waveshape without substantially altering the amplitude of the periodic electrical signals regardless of the principal frequency, said tone enhancement means having an input coupled to the output of said oscillator and including:
• an amplifier having an input,
• an input diode having a frequency dependent impedance and coupled between ground and the input of the tone enhancement means,
• and a capacitor coupled between the inputs of the tone enhancement means and the amplifier wherein said periodic electrical signals tend to be frequency split across the impedance of said capacitor and the frequency dependent impedance of said diode means, for inverting and coupling said periodic electrical signals across said diode to said amplifier input;
• and
• audio means for generating an audible signal in response to said altered periodic signal coupled to said tone enhancement means.

In a musical instrument, a circuit comprising:

• a plurality of discrete resistive elements, each having a contact node coupled thereto;
• conductive wire means for selectively coupling with at least one of said contact nodes;
• an oscillator coupled to said plurality of discrete resistive elements and said conductive wire means to selectively generate a plurality of periodic electrical signals each having a distinct principal frequency;
• and a distinct waveshape definable by a combination of a plurality of sine waves having a frequency spectrum;
• tone enhancement means for selectively altering the frequency spectrum of the plurality of sine waves defining the waveshape for modifying the waveshape of the periodic electrical signals without substantially altering the amplitude of the periodic electrical signals regardless of the principal frequency, said tone enhancement means having an input coupled to the output of said oscillator and including:
• an amplifier having an input,
• a first input diode coupled between ground and the input of the tone enhancement means and having a first preferred direction of conductivity, and
• a second input diode coupled between the input of the amplifier and the tone enhancement means input, said second input diode having a second preferred direction of conductivity opposite to said first direction, a source of variable bias voltage coupled to the input of the tone enhancement means, and
• means coupled between the first diode and the amplifier input for inverting and coupling the voltage across said first diode to said amplifier;
• and
• audio means for generating an audible signal in response to said altered periodic signal coupled to said tone enhancement means.

In a musical instrument, a circuit comprising:

• a plurality of discrete resistive elements, each having a contact node coupled thereto;
• conductive wire means for selectively coupling with at least one of asid contact nodes;
• an oscillator coupled to said plurality of discrete resistive elements and said conductive wire means to selectively generate a plurality of periodic electrical signals each having a distinct principal frequency;
• and a distinct waveshape definable by the combination of a plurality of sine waves having a frequency spectrum;
• tone enhancement means for selectively altering the frequency spectrum of the plurality of the sine waves defining the waveshape of the periodic electrical signals for modifying the waveshape without substantially altering the amplitude of the periodic electrical signal regardless of the principal frequency, said tone enhancement means having an input coupled to the output of said oscillator;
• and
• audio means for generating an audible signal in response to said altered periodic signal coupled to said tone enhancement means;
• said enhancement means including:
• a voltage controlled waveshaping circuit coupled to said oscillator;
• a voltage controlled phase shifting circuit coupled to said waveshaping circuit;
• and
• a voltage controlled amplifier coupled to said phase shifting circuit;
• and
• a variable modulating oscillator having an input selectively coupled to said waveshaping circuit for timbrato, to said phase shifting circuit for phasing, to said voltage controlled amplifier for tremolo and to said oscillator for vibrato modulation.