ar comb asig, krvt, ilpt[, istor]
ar alpass asig, krvt, ilpt[, istor]
ar reverb asig, krvt[, istor]
An input signal is reverberated for krvt seconds with "colored" (comb), flat (alpass), or "natural room" (reverb) frequency response.
istor (optional) - initial disposition of delay-loop data space ( cf. reson). The default value is 0.
A standard reverb unit is composed of four comb filters in parallel followed by two alpass units in series. Looptimes are set for optimal "natural room response." Core storage requirements for this unit are proportional only to the sampling rate, each unit requiring approximately 3K words for every 10KC. The comb, alpass, delay, tone and other Csound units provide the means for experimenting with alternate reverberator designs
Since output from the standard reverb will begin to appear only after 1/20 second or so of delay, and often with less than three-fourths of the original power, it is normal to output both the source and the reverberated signal. Also, since the reverberated sound will persist long after the cessation of source events, it is normal to put reverb in a separate instrument to which sound is passed via a global variable, and to leave that instrument running throughout the performance.
Example:
ga1 init 0 ; init an audio receiver/mixer
instr 1 ; instr (there may be many copies)
a1 oscili 8000, cpspch(p5), 1 ; generate a source signal
out a1 ; output the direct sound
ga1 = ga1 + a1 ; and add to audio receiver
endin
instr 99 ; (highest instr number executed last)
a3 reverb ga1, 1.5 ; reverberate whatever is in ga1
out a3 ; and output the result
ga1 = 0 ; empty the receiver for the next pass
endin