Musical tone generator system using multiple frequency synthesizers

Claim 1

A tone generator system for an electrical musical instrument, said system comprising, at least first and second frequency synthesizers, one for each of two related octaves, each having an input terminal and a plurality of output terminals, and each being operative to divide the frequency of a signal of appropriate frequency applied to its input terminal to produce at its output terminals a like plurality of pitches corresponding to different notes of the musical scale, said at least first and second frequency synthesizers having like frequency dividing factors associated with like output terminals so as to be operative in response to application thereto of input signals of the same frequency to produce the same pitches at corresponding output terminals thereof, a first source of clock pulses connected to the input terminal of said first frequency synthesizer, said first source having a frequency to produce at a given plurality of the output terminals of said first synthesizer a like plurality of notes of the musical scale in one octave, which notes inherently have slight errors in frequency from corresponding notes of the true equitempered scale which differ in sense and degree from note to note as a function of its frequency dividing factors, and a second source of clock pulses connected to the input terminal of said second frequency synthesizer, the frequency of said second source differing from the frequency of said first source by a factor which differs from a power of two by one or more nominal semitones such that said second frequency synthesizer is operative in response to clock pulses from said second source to produce at the plurality of output terminals of said second synthesizer corresponding to the said given plurality of output terminals of said first synthesizer, a like plurality of notes in a related octave which individually are octavely unrelated to the notes produced at like output terminals of said first synthesizer, which notes also inherently have slight errors in frequency from the true equitempered scale which differ in sense and degree from note to note, with the error from true equitemperament appearing at a given output terminal of said second synthesizer being of the same sense and magnitude as the error from true equitemperament appearing on the corresponding output terminal of said first synthesizer, whereby, because different notes appear on corresponding output terminals of said first and second frequency synthesizers, temperament interval errors inherent in said first and second frequency synthesizers are randomized.