Tone generation system employing triangular waves

In a musical tone source of the kind having a first waveshape generator which includes means for generating a first ascending series of quantities and means responsive to said series of quantities to produce a sequence of analog wave amplitudes each of which is a function of a respective one of said quantities;

• the improvement comprising:
• a second waveshape generator which includes means for generating a second ascending series of quantities, at least one of said means for generating an ascending series of quantities including a digital adder and means causing said adder to add a digital musical scale value repetitively to produce said ascending series of quantities, said adder including means for receiving a digital carry input;
• combining means cooperating with said analog wave amplitude producing means to produce a sequence of analog wave amplitudes each of which is a function of the sum of a respective pair of said quantities of said first and second series respectively;
• and
• means for applying a digital carry input to said receiving means of said adder for creating a differential between the respective rates of ascent of said first and second series of quantities, whereby to produce a chorus effect.

In a triangular waveform generator of the type including means for representing a musical scale value, means for adding said musical scale value repetitively to produce an ascending series of quantities, means for periodically reversing the direction of change of said quantities to produce an alternately ascending and descending series thereof, and means responsive to said alternately ascending and descending series of quantities to produce a sequence of analog wave amplitudes each of which is a function of a respective one of said quantities;

• the improvement wherein:
• said means for adding said musical scale value comprises an adder having a carry output and a latch which is arranged to store said ascending series of quantities and the carry output of said adder;
• and
• said means for periodically reversing the direction of change includes means for inverting said series of quantities whereby to reverse the ascent thereof, said inverting means being capable of being enabled and disabled, bistable means connected to enable said inverting means in one of its states and to disable said inverting means in its other state, and means coupling said adder carry output to switch said bistable means back and forth on respective alternate carries of said adder.

A plural footage chorusing musical tone source comprising:

• means for representing a selected musical scale value;
• at least two waveshape generators clocked at the same effective rate, each of the type having an input and including means for generating an ascending series of quantities by repetitively adding respective values received at said inputs;
• means responsive to said musical scale value representing means to connect to one of said waveshape generator inputs a musical scale value related to said selected value, and to the other of said waveshape generator inputs a musical scale value which differs from said related value by a factor of two, whereby the frequencies of the respective waveshapes generated thereby are octavely related;
• and
• means for introducing the same selected arithmetic correction into both of said ascending series of quantities, whereby the respective effects of said correction on said two series are different in porportion to said two waveshape frequencies, so as to produce a chorus differential between said two frequencies.

A polyphonic musical instrument comprising:

• means for selecting one from among a plurality of musical notes to be sounded;
• first means, responsive to the selection of a single note by said note-selecting means, for representing the musical scale value of the selected note;
• one or more second means, each responsive to said first value-representing means, to derive respective representations of the musical scale values of one or more footage notes respectively related by one or more octaves to the selected note;
• a plurality of means, responsive to said first, and each of said second, value-representing means respectively, to repetitively add said selected note musical scale value and said footage note musical scale values respectively, whereby to generate respective ascending series of quantities;
• respective means for periodically reversing said ascending series whereby to produce respective alternately ascending and descending series of quantities representing successions of amplitudes of respective periodic waveforms of octavely related frequencies;
• summing means for combining said respective series of quantities, whereby to derive a single series of sum quantities representing a combined waveform;
• and
• output means responsive to said series of sum quantities to produce a series of analog wave amplitudes corresponding respectively thereto.