;;; Moog style four pole lowpass filter clm unit generator
;;; low pass, 24db/Oct, variable resonance, warm, analog sound ;-)
;;; [all this digital wizardry and we're back where we started!]
;;;
;;; original C instrument by Tim Stilson
;;; translation into clm and tuning by
;;; Fernando Lopez-Lezcano, nando@ccrma.stanford.edu
;;; http://ccrma.stanford.edu/~nando/clm/moog
;;;
;;; translated to Snd scheme function by Bill,
;;; changed 17-Apr-05 to use def-clm-struct (for the optimizer's benefit)
(provide 'snd-moog.scm)
(if (not (provided? 'snd-env.scm)) (load-from-path "env.scm"))
(if (not (provided? 'snd-ws.scm)) (load-from-path "ws.scm"))
(define moog-gaintable (vct 0.999969 0.990082 0.980347 0.970764 0.961304 0.951996 0.94281 0.933777 0.924866 0.916077
0.90741 0.898865 0.890442 0.882141 0.873962 0.865906 0.857941 0.850067 0.842346 0.834686
0.827148 0.819733 0.812378 0.805145 0.798004 0.790955 0.783997 0.77713 0.770355 0.763672
0.75708 0.75058 0.744141 0.737793 0.731537 0.725342 0.719238 0.713196 0.707245 0.701355
0.695557 0.689819 0.684174 0.678558 0.673035 0.667572 0.66217 0.65686 0.651581 0.646393
0.641235 0.636169 0.631134 0.62619 0.621277 0.616425 0.611633 0.606903 0.602234 0.597626
0.593048 0.588531 0.584045 0.579651 0.575287 0.570953 0.566681 0.562469 0.558289 0.554169
0.550079 0.546051 0.542053 0.538116 0.53421 0.530334 0.52652 0.522736 0.518982 0.515289
0.511627 0.507996 0.504425 0.500885 0.497375 0.493896 0.490448 0.487061 0.483704 0.480377
0.477081 0.473816 0.470581 0.467377 0.464203 0.46109 0.457977 0.454926 0.451874 0.448883
0.445892 0.442932 0.440033 0.437134 0.434265 0.431427 0.428619 0.425842 0.423096 0.42038
0.417664 0.415009 0.412354 0.409729 0.407135 0.404572 0.402008 0.399506 0.397003 0.394501
0.392059 0.389618 0.387207 0.384827 0.382477 0.380127 0.377808 0.375488 0.37323 0.370972
0.368713 0.366516 0.364319 0.362122 0.359985 0.357849 0.355713 0.353607 0.351532 0.349457
0.347412 0.345398 0.343384 0.34137 0.339417 0.337463 0.33551 0.333588 0.331665 0.329773
0.327911 0.32605 0.324188 0.322357 0.320557 0.318756 0.316986 0.315216 0.313446 0.311707
0.309998 0.308289 0.30658 0.304901 0.303223 0.301575 0.299927 0.298309 0.296692 0.295074
0.293488 0.291931 0.290375 0.288818 0.287262 0.285736 0.284241 0.282715 0.28125 0.279755
0.27829 0.276825 0.275391 0.273956 0.272552 0.271118 0.269745 0.268341 0.266968 0.265594
0.264252 0.262909 0.261566 0.260223 0.258911 0.257599 0.256317 0.255035 0.25375))
(define moog-freqtable
'(0 -1
0.03311111 -0.9
0.06457143 -0.8
0.0960272 -0.7
0.127483 -0.6
0.1605941 -0.5
0.1920544 -0.4
0.22682086 -0.3
0.2615873 -0.2
0.29801363 -0.1
0.33278003 -0.0
0.37086168 0.1
0.40893877 0.2
0.4536417 0.3
0.5 0.4
0.5463583 0.5
0.5943719 0.6
0.6556281 0.7
0.72185487 0.8
0.8096009 0.9
0.87913835 0.95
0.9933787 1
1 1))
;;; moog struct is a list (freq res arr a)
;;; freq: cutoff frequency in Hertz
;;; Q: resonance, 0->no resonance, 1->oscilates at freq
;;;
;;; Note: the relation between freq and the actual cutoff is not exactly linear but
;;; I prefered to translate Hz into the internal parameter rather than controlling
;;; the cutoff frequency in terms of a number that goes between -1 and 1.
(def-clm-struct moog
(freq 0.0 :type float)
(Q 0.0 :type float)
(s #f :type vct)
(y 0.0 :type float)
(fc 0.0 :type float))
(define (make-moog-filter frequency Q)
"(make-moog-filter frequency Q) makes a new moog-filter generator. 'frequency' is the cutoff in Hz,
'Q' sets the resonance: 0 = no resonance, 1: oscillates at 'frequency'"
(make-moog :freq frequency
:Q Q
:s (make-vct 4)
:y 0.0
:fc (envelope-interp (/ frequency (* (mus-srate) 0.5)) moog-freqtable)))
(define moog-frequency
(make-procedure-with-setter
(lambda (gen)
(moog-freq gen))
(lambda (gen frq)
(set! (moog-freq gen) frq)
(set! (moog-fc gen) (envelope-interp (/ frq (* (mus-srate) 0.5)) moog-freqtable)))))
(define (moog-filter m sig)
;"(moog-filter m sig) is the generator associated with make-moog-filter"
(let ((A (* 0.25 (- sig (moog-y m))))
(st 0.0))
(do ((cell 0 (1+ cell)))
((= cell 4))
(set! st (vct-ref (moog-s m) cell))
(set! A (min (max -0.95 (+ A (* (moog-fc m) (- A st)))) 0.95))
(vct-set! (moog-s m) cell A)
(set! A (min (max -0.95 (+ A st)) 0.95)))
(let* ((ix (* (moog-fc m) 99.0))
(ixint (inexact->exact (floor ix)))
(ixfrac (- ix ixint)))
(set! (moog-y m) (* A (moog-Q m)
(+ (* (- 1 ixfrac)
(vct-ref moog-gaintable (+ ixint 99)))
(* ixfrac (vct-ref moog-gaintable (+ ixint 100)))))))
A))
;;; (define gen (make-moog-filter 500.0 .1))
;;; (map-channel (lambda (y) (moog-filter gen y)))
;;; (run (lambda () (moog-filter gen 1.0)))
