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Schroeders Reverberator [CSound]
Definition for reverberation time: Time until the sound has decreased to 0.1% of the original amplitude.
The original signal is piped through 4 parallel comb filters then through 2 serial all-pass filters.
Comb delay times are relatively prime to one another (0.031, 0.037, 0.041, 0.043)
The all-pass filters have delays between 0.005 and 0.02 seconds. The make the echo density. The first all-pass turns each comb echo into a series
The orc file
gareverberation init 0 instr X ; asig somehow being produced here gareverberation = gareverberation + asig endin instr 99 idur = p3 igain = p4 ; gain to control amplitude, 0 <= igain <= 1 irevtime = p5 ; reverberat time ireverb = p6 ; percent reverberated signal, 0 <= ireverb <= 1 iacoustic = 1 - ireverb ; pct unreverberated p3 = p3+irevtime+.1 inorm = .91999 ; constant to normalize the tone ; ; make sure gain is between 0 and 1 (1 = 100%) ; igain = (igain <= 0 ? .01 : igain) ; igain = (igain > 1.0 ? 1.0 : igain) ; make sure % reverb between 0 and 1 (0 ok, 1=100%) ;ireverb = (ireverb > .99 ? .99 : ireverb) ;ireverb = (ireverb < 0 ? 0 : ireverb) iacoustic = 1 - ireverb ; percent unreverberated ac1 comb gareverberation, irevtime, .0297 ac2 comb gareverberation, irevtime, .0371 ac3 comb gareverberation, irevtime, .0411 ac4 comb gareverberation, irevtime, .0437 acomb = ac1 + ac2 + ac3 + ac4 ap1 alpass acomb, .09683, .005 arev alpass ap1, .03292, .0017 ; mix signal (percent acoustic and percent reverbed) aout = (iacoustic * gareverberation) + (ireverb * arev) ; attenuate and output the signal out aout*igain/inorm gareverberation = 0 endin
The signal might be piped through a low pass filter at the end to make it sound less metallic.