Keyboard-controlled digital playback of an organ-pipe tone
A. W. Nolle · The Journal of the Acoustical Society of America · 1982
The tone sample in computer memory includes the attack, ten or more periods of “steady” state, and the decay. With well-known programming techniques and digital-analog equipment, it is simple to make the sample audible. This paper considers the problem of prolonging the tone as long as the key is down without unduly increasing memory requirements. Repetition of one cycle gives the unvarying wave form of a stable electronic generator. This may be acceptable for reed pipe tones, but for flue pipe tones the absence of the small spectral fluctuations of the original source is evident. The indefinite repetition of, say, ten periods of the original tone reintroduces fluctuations, but the regular flyback may be detectable unless the original is a nearly fixed waveform. A better solution is to execute a flyback of NF periods at the end of the “steady” sample, where the integer NF is a random number that ranges from unity to the full length of the “steady” sample. Taperecorded demonstration tones will be played. A tone with tremulant can be handled by using a constant NF.