Process for forming musical tones

A process for forming musical tones comprising:

• a first load step in which a first waveshape signal, a second waveshape signal, and a third waveshape signal are added to generate a fourth waveshape signal which is loaded to the first half of a first memory means, said first waveshape signal being read out from said first half of said first memory means prior to loading therein of said fourth waveshape signal, said second waveshape signal being the signal read out from a second memory means, said third waveshape signal being an input waveshape signal to be formed into a musical tone
• a transfer step in which data stored in the second half of said first memory means is transferred to said second memory means after said first load step;
• a clearing step in which said second half of said first memory means is loaded by zero after said transfer step;
• a step of generating a third spectrum signal by transforming the contents of said first memory means after said clearing step to a frequency spectrum by the Fourier Transform operation;
• a step of generating a fourth spectrum signal by multiplying said third spectrum signal by a first transfer function on a frequency domain;
• a second load step in which said fourth spectrum signal is transformed to a function of time by the Inverse the first and second halves of Fourier Transform operation, the result being stored said first memory means in place of the prior contents thereof;
• a step of repeatedly generating said fourth waveshape signal by repeating said first load step, said transfer step, said clearing step, and said second load step in a cyclic order;
• and
• a step of generating a waveshape and tone having a designated frequency in accordance with said fourth waveshape signal.

Apparatus for forming musical tones, comprising:

• means for repetitively providing during successive time intervals T.sub.o an amplitude sampled time domain source waveshape signal V.sub.m (n),
• first memory means for storing amplitude samples of a time domain first waveshape signal y.sub.m (l),
• transform means, operative once each time interval T.sub.o, for transforming said stored first waveshape signal to the corresponding frequency domain spectrum signal y.sub.m (k), for modifying said corresponding spectrum signal by a frequency domain transfer function H(k), and for inversely transforming the modified corresponding spectrum signal U.sub.m (k) back to the time domain to produce an amplitude sampled time domain second waveshape signal U.sub.m (l),
• delay means for storing a certain portion U.sub.m (N+n) of said second waveshape signal until a later time interval T.sub.o,
• combining means, operative during each time interval T.sub.o, for combining the source waveshape signal V.sub.m (n) provided during the current time interval, a different portion U.sub.m (n) of said second waveshape signal, and the stored certain portion U.sub.m-l (N+n) of said second waveshape signal from a prior time interval T.sub.o to produce an amplitude sampled time domain output waveshape signal Y.sub.m (n), said output waveshape signal also being stored in said first memory means as part of said first waveshape signal Y.sub.m (l), and
• means for producing musical tones from said output waveshape signal.

Apparatus for forming musical tones, comprising:

• means for storing, at each of successive time intervals, a time domain first waveshape signal having a set of 2N amplitude samples, the amplitude samples of the second half of said first waveshape signal all being zero,
• frequency domain modification means, operative each time interval, for transforming said first waveshape signal to the frequency domain, modifying the resultant frequency domain signal, and inversely transforming the modified frequency domain signal to form a time domain second waveshape signal having a set of 2N amplitude samples, at least some of the amplitude samples in the second half of said second waveshape signal being non-zero,
• means for generating a time domain resultant waveshape signal having N amplitude samples by utilizing the sampled amplitudes of the first half of the second waveshape signal formed during one time interval combined with the amplitude samples of the second half of the second waveshape signal formed during a prior time interval, the amplitude samples of said resultant waveshape signal also being supplied to said storing means for use as the amplitude samples of the first half of said first waveshape signal, and
• means for converting said resultant waveshape signal to a musical tone.