Data compressing and expanding apparatus for tone generation

An electronic musical instrument comprising:

• differential value quantizing means for sequentially quantizing differential values each between adjacent sampled values of a received sampled value signal, and for sequentially adding quantizing errors each produced when a differential value is quantized to corresponding first differential values to be next quantized sequentially;
• lower significant bit separating means for sequentially separating respective groups of lower significant n bits of the first differential values quantized by said differential value quantizing means when the respective first differential values are quantized with n being a natural number equal to or larger than 2 to obtain corresponding second differential values, and for sequentially adding respective groups of separated n bits to corresponding first differential values to be next processed sequentially;
• adaptive quantizing means for causing each of the obtained second differential values to be subjected to adaptive quantization to obtain an adaptive quantized value, and for adding a quantizing error produced in the adaptive quantization by decoding the adaptive quantized value to the corresponding second differential value to be next subjected to adaptive quantization;
• storage means for storing the adaptive quantized value obtained by said adaptive quantizing means;
• a performance operator for designating a pitch of a tone to be generated;
• and
• tone signal generating means for sequentially reading out adaptive quantized values stored in said storage means on the basis of a frequency corresponding to the pitch designated by said performance operator, for decoding the second differential values from the read-out adaptive quantized values, for sequentially accumulating the decoded second differential values by 2.sup.n times at a period corresponding to 1/2.sup.n of the sampling period of the received signal, and for outputting the resulting signal to generate a tone signal.