Back to results
US 4,351,219 AGranted
Digital tone generation system utilizing fixed duration time functions
AssigneeKimball International, Inc.
InventorSteven C. Bass
Life of this patent
Estimating the term…
Abstract
A tone generation system intended primarily for use in electronic musical instruments wherein a digital representation of a harmonically rich waveform is sampled, and a musical tone is produced therefrom. The stored waveform could be the four term Blackman-Harris window function, which has negligible side lobes and thus greatly attenuated higher harmonics. The stored function is read out at a fixed rate, but the time periods between successive readings of the waveform are varied to thereby vary the frequency of the output signal.
Claims22
An electronic musical instrument comprising:
- player actuated tone frequency selection means, memory means for storing one cycle of a fixed width window function waveform, means responsive to the actuation of the tone selection means for reading said waveform out of said memory means at a fixed rate for each cycle thereof independent of the frequency selected and and in a repetitive fashion to produce a continuous signal wherein the period of time between each successive reading of a cycle of the waveform is selectively adjusted in response to the frequency selected by the tone selection means without changing the width of the read out waveform to thereby produce a continuous train of time sequential said window function waveforms having a frequency proportional to the period of time between each successive reading, and means responsive to the train of read out waveforms for filtering said train to produce a musical tone.
An electronic musical instrument comprising:
- a keyboard comprising a plurality of playing keys assigned to different tone frequencies, memory means for storing one cycle of a window function waveform, means responsive to the actuation of any key of the keyboard for reading said waveform out of said memory means at a fixed rate for each read out cycle thereof to produce a read out waveform of a predetermined constant width and in a repetitive fashion to produce a continuous signal as long as said any one key is held actuated and for adjusting the period of time between the beginning of each reading of the waveform and the beginning of the next reading thereof in the continuous signal in response to the tone frequency of the actuated key without changing the width of the read out waveform from said predetermined constant width, and means responsive to the read out window function waveforms for filtering said waveforms to produce a musical tone.
An electronic musical instrument for producing tones of selected diverse frequencies comprising:
- memory means for storing one cycle of a harmonically-rich waveform;
- means for reading said waveform out of said memory means at a fixed rate and in repetitive manner wherein the period of time between successive operable readings of the waveform is selectively adjusted dependent on the selected frequency to thereby produce an output signal comprising a train of said waveforms wherein each waveform has a fixed width independent of the selected frequency and is separated from adjacent waveforms by time intervals in which a zero signal level is present equal to the period of time between the respective successive operable readings of the stored waveform;
- said train of waveforms comprising a plurality of cyclically recurring series each having a fixed number of said waveforms, and including means for controlling the harmonic content of the waveform train comprising means for adjusting independently of each other the respective amplitudes of the individual waveforms in each series;
- and
- means responsible to said output signal for producing an audible tone having a pitch inversely proportional to the period of time between successive operable readings of the stored waveform.
2 more elements
A method of generating a musical tone comprising:
- providing a memory in which a representation of one cycle of a waveform is stored,
- addressing the memory to read the stored representation of the waveform always at a fixed rate and repetitively but selectively varying the period of time between successive readings of the waveform to vary the frequency of the tone to produce a waveform train comprising a series of the read out waveforms that is cyclically repeated and wherein the waveforms are separated by said period of time,
- controlling the harmonic content of the waveform train by scaling the amplitudes of the respective individual waveforms in each series independently of each other, and
- producing a musical tone from the scaled waveform train wherein the fundamental pitch of the tone varies as the period of time between successive waveforms is varied.
1 more element
Dependencies are inferred from the claim text.