- Rockin’ Patent®: US Patent No. 4,018,121
- Filed: 2 May 1975
- In the name of: (The Board of Trustees of) Leland Stanford Junior University
- Title: Method Of Synthesizing A Musical Sound
- What’s claimed: “A method of synthesizing a musical sound composed of a plurality of component frequencies and characterized by a time-varying amplitude envelope having a time-varying attack portion, a substantially steady-state portion and a time-varying decay portion, the steps comprising, generating a signal ωc to define a carrier frequency in the audio range, generating a signal ωm to define a modulation frequency in the audio range, generating a signal I(t) to define a time-varying modulation index, frequency modulating ωc with ωm to form a frequency modulated wave defined by e = Asin [ωc t + I(t) sin ωm t] where e defines the instantaneous amplitude of said wave, A defines the peak amplitude of said wave, and [ωc t + I(t) sin ωm t] defines the frequency spectrum of said wave wherein the frequency spectrum of said wave changes as a function of the modulation index I(t) to form a representation of said sound.”
- Why this patent rocks: This blog by -ajxs suggests that this patent appears to relate to the frequency modulation synthesis technology that forms the basis of the Yamaha DX7 synthesiser. For a detailed technical analysis of the technology and the engineering of the Yamaha DX7, see here.
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