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;; CLM implementation of Xenakis' Dynamic Stochastic Synthesis as heard in
;; his GENDY3, S.709, Legende d'Eer, etc.
;; 12/17/03
;; revised 01/22/06
;; Bill Sack wsack@buffalo.edu
;; revised slightly to accommodate the run macro, Bill 13-Jun-06
(if (provided? 'snd)
(require snd-ws.scm)
(require sndlib-ws.scm))
(require snd-env.scm)
(definstrument
(stochastic start dur
(amp .9) (bits 16) (xmin 1) (xmax 20) (xwig 0) (xstep 1) (ywig 0) (xfb 0)
(init-array '((10 0) (10 1) (10 0) (10 -.7) (10 0) (10 .5)
(10 0) (10 -.3) (10 0) (10 .2) (10 0) (10 -.1))))
;;some explanation of the parameters:
;;amp - scales overall amplitude
;;bits - the resolution of the wave's amplitude dimension
;;xmin - minimum number of samples between time breakpoints. must be equal to or greater than 1
;;xmax - maximum number of samples between time breakpoints.
;;xwig - amplitude applied to random walk function in time dimension
;;xstep - quantization of freedom in time dimension, in samples. minimum of 1
;;ywig - amplitude applied to random walk function in amplitude dimension, in
;; percent of overall possible amplitude
;;xfb - an attempt at an FIR low-pass filter - the old (n + (x * n-1)) trick,
;; not really that useful
;;init-array - initial x and y breakpoints for wave. x values must be
;; integers and 1 or greater, y values between -1.0 and 1.0
(let* ((beg (seconds->samples start))
(end (+ beg (seconds->samples dur))))
(let ((d-click (make-env (list 0 1 (- end 100) 1 end 0) :duration dur))
;;make float-vector to hold x,y breakpoints
(xy-array (make-float-vector (* (length init-array) 2)))
(y 0.0)
(dx 0)
(prev-dx 0)
(dy 0.0)
(j 0.0)
(m 0)
(dt 0)
(output 0.0)
(oldy 0.0)
(xdev 0)
(ydev 0)
(b (expt 2 (- bits 1)))
(xy-array-l (* (length init-array) 2)))
;;fill xy-array with values from init-array
(do ((iy 0 (+ iy 2));;index for reading values from init-array (a 2-dimensional list)
(jy 0 (+ jy 1)));;index for writing to xy-array (a 1-dimensional float-vector)
((= iy xy-array-l))
(set! (xy-array iy) ((init-array jy) 0))
(set! (xy-array (+ iy 1))
;;convert signed float y values into signed integers
(floor (* b
((init-array jy) 1)))))
(do ((i beg (+ i 1)))
((= i end))
(when (= dx dt);;when current sample is a breakpoint
(set! dx (floor (xy-array (modulo m xy-array-l))))
(set! y (xy-array (+ (modulo m xy-array-l) 1)))
(set! prev-dx (floor (xy-array (modulo (- m 2) xy-array-l))))
(set! dy (- y oldy))
(set! oldy y)
;;straight uniform distribution for y
(set! ydev (round (mus-random (* .01 b ywig))))
;;gaussian distribution for x
(set! xdev
(* xstep (round
(* xwig
(sqrt (* -2.0 (log (- 1 (random 1.0))))) ; ??
(cos (random 6.283185307179586))))))
(set! (xy-array (modulo m xy-array-l))
;;mirror stuff for x
(if (>= (round xmax) (+ dx xdev) (round xmin))
(round (+ (* xfb prev-dx)
(* (- 1 xfb) (+ dx xdev))))
(max (min (round (+ (* xfb prev-dx)
(* (- 1 xfb) (- dx xdev))))
(round xmax))
(round xmin))))
(set! (xy-array (+ (modulo m xy-array-l) 1))
;;mirror stuff for y
(if (>= b (+ y ydev) (- b))
(+ y ydev)
(max (min (- y ydev) b) (- b))))
(set! m (+ m 2))
(set! dt 0))
(set! dt (+ dt 1))
(set! j (+ j (/ dy dx)));linear interpolation
(set! output (/ j b));normalization -1 to 1
(outa i (* amp output (env d-click)))))))
;(with-sound (:statistics #t)(stochastic 0 10 :xwig .25 :ywig 10.0))
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