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;;; NREV (the most popular Samson box reverb)
(provide 'snd-nrev.scm)
(if (provided? 'snd)
(require snd-ws.scm)
(require sndlib-ws.scm))
(definstrument (nrev (reverb-factor 1.09) (lp-coeff 0.7) (volume 1.0))
;; reverb-factor controls the length of the decay -- it should not exceed (/ 1.0 .823)
;; lp-coeff controls the strength of the low pass filter inserted in the feedback loop
;; output-scale can be used to boost the reverb output
(let ((dly-len (if (= (floor *clm-srate*) 44100)
#i(2467 2753 3217 3533 3877 4127 599 197 67 101 97 73 67 53 37)
(and (= (floor *clm-srate*) 22050)
#i(1237 1381 1607 1777 1949 2063 307 97 31 53 47 37 31 29 17))))
(chan2 (> (channels *output*) 1))
(chan4 (= (channels *output*) 4)))
(if (not dly-len)
(let ((srscale (/ *clm-srate* 25641))
(next-prime (lambda (val)
(do ((val val (+ val 2)))
((or (= val 2)
(and (odd? val)
(do ((i 3 (+ i 2))
(lim (sqrt val)))
((or (= 0 (modulo val i))
(> i lim))
(> i lim)))))
val)))))
(set! dly-len #i(1433 1601 1867 2053 2251 2399 347 113 37 59 53 43 37 29 19))
(do ((i 0 (+ i 1)))
((= i 15))
(let ((val (floor (* srscale (dly-len i)))))
(if (even? val) (set! val (+ val 1)))
(set! (dly-len i) (next-prime val))))))
(let* ((len (+ (floor *clm-srate*) (framples *reverb*)))
(comb1 (make-comb (* .822 reverb-factor) (dly-len 0)))
(comb2 (make-comb (* .802 reverb-factor) (dly-len 1)))
(comb3 (make-comb (* .773 reverb-factor) (dly-len 2)))
(comb4 (make-comb (* .753 reverb-factor) (dly-len 3)))
(comb5 (make-comb (* .753 reverb-factor) (dly-len 4)))
(comb6 (make-comb (* .733 reverb-factor) (dly-len 5)))
(low (make-one-pole lp-coeff (- lp-coeff 1.0)))
(allpass1 (make-all-pass -0.700 0.700 (dly-len 6)))
(allpass2 (make-all-pass -0.700 0.700 (dly-len 7)))
(allpass3 (make-all-pass -0.700 0.700 (dly-len 8)))
(allpass4 (make-all-pass -0.700 0.700 (dly-len 9))) ; 10 for quad
(allpass5 (make-all-pass -0.700 0.700 (dly-len 11)))
(allpass6 (and chan2 (make-all-pass -0.700 0.700 (dly-len 12))))
(allpass7 (and chan4 (make-all-pass -0.700 0.700 (dly-len 13))))
(allpass8 (and chan4 (make-all-pass -0.700 0.700 (dly-len 14))))
(filts (if (not chan2)
(vector allpass5)
(if (not chan4)
(vector allpass5 allpass6)
(vector allpass5 allpass6 allpass7 allpass8))))
(combs (make-comb-bank (vector comb1 comb2 comb3 comb4 comb5 comb6)))
(allpasses (make-all-pass-bank (vector allpass1 allpass2 allpass3))))
(if chan4
(do ((i 0 (+ i 1)))
((= i len))
(out-bank filts i
(all-pass allpass4
(one-pole low
(all-pass-bank allpasses
(comb-bank combs (* volume (ina i *reverb*))))))))
(if chan2
(let ((gen1 (filts 0))
(gen2 (filts 1)))
(do ((i 0 (+ i 1)))
((= i len))
(let ((val (all-pass allpass4
(one-pole low
(all-pass-bank allpasses
(comb-bank combs (* volume (ina i *reverb*))))))))
(outa i (all-pass gen1 val))
(outb i (all-pass gen2 val)))))
(let ((gen (filts 0)))
(do ((i 0 (+ i 1)))
((= i len))
(outa i (all-pass gen
(all-pass allpass4
(one-pole low
(all-pass-bank allpasses
(comb-bank combs (* volume (ina i *reverb*)))))))))))))))
;;; (with-sound (:reverb nrev) (outa 0 .1) (outa 0 .5 *reverb*))
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