| 摘要 |
<p>In a generator of musical notes for use as an electronic organ or other instrument, particularly of keyboard type, a computer is programmed to provide control and data signals to external hardware in response to the selection of stops and keys. In response to each change of stop a range of characteristic harmonic structures is synthesised digitally to provide singlecycle reference waveforms for storage for so long as that stop remains in use. In response to the selection of a key in that stop an appropriate reference waveform is sampled, or interpolative sampling is performed between two waveforms, so that an harmonic structure is produced by sampling which is precisely related to the position of the key in the register. The pitch of the note to be reproduced from the digital samples is determined by the rate of sampling which can be finely resolved. Samples are read at a fixed clock rate, but the number of clock intervals required to step through the single-cycle reference waveform is caused to be inversely proportional to the required pitch. Many independent notes can be produced simultaneously for audio-reproduction following digital-to-analogue conversion of the sample values.</p> |
