Asynchronous waveform generating device for use in an electronic musical instrument

A waveform generating device, comprising:

• storing means for storing sampled waveform data, said data comprising samples of a fundamental waveform,
• pitch designation means for generating a pitch signal indicating the pitch of a musical tone to be generated,
• readout means for reading said waveform data at a first speed, said readout means including address generating means for generating addresses for the storing means that are determined based on the pitch signal,
• interpolation means for calculating intermediate data between two sample data consecutively read out by said readout means and for outputting said intermediate data at a predetermined sampling cycle, said intermediate data corresponding to hypothetical sample values of said waveform at a regeneration sampling rate different from the predetermined fundamental sampling rate,
• beginning readout designation means for designating the beginning of readout by said readout means, and
• readout speed control means for setting the speed of said readout means to a second speed higher than the first speed during a time interval beginning at the designation of the beginning of readout by said beginning readout designation means and continuing until a predetermined number of samples have been read out by said readout means, to quickly obtain sample data necessary for the interpolation calculation and thereby reduce a time lag between the designation of the beginning of readout and the outputting of said intermediate data.

A waveform generating device, comprising:

• first storing means for storing samples waveform data, said data comprising samples of a fundamental waveform that have been encoded by means of differential pulse code modulation,
• pitch designation means for outputting a pitch signal indicating the pitch of a musical tone to be generated,
• repetition designation means for generating a repetition signal corresponding to a characteristic of the musical tone to be generated,
• readout means for reading said waveform data out of said first storing means, including address generating means for generating addresses of samples waveform data to be read out, said addresses being based on said pitch signal, said address generating means repetitively addressing a loop portion of the waveform data,
• decoding means for decoding said samples and consecutively outputting decoded sample data,
• second storing means for storing said part of the readout decoded sample data corresponding to a header of the loop portion in a fixed sequence,
• interpolation means for calculating intermediate data between two consecutive decoded sample data and for outputting said intermediate data, said intermediate data corresponding to samples of said fundamental waveform at a rate of one sample per a hypothetical regeneration sampling interval based on the pitch of the musical tone to be generated, and
• loop repetition means for reading successive values of decoded loop header sample data out of said second storing means and outputting said decoded sample data to said interpolation means to be used for interpolation of intermediate data between sample data located near an end of said loop portion for a number of repetitions based on said repetition signal.