Steve's updated delay.ny (http://bugzilla.audacityteam.org/show_bug.cgi?id=533)
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;type process
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;categories "http://lv2plug.in/ns/lv2core#DelayPlugin"
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;name "Delay..."
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;action "Performing Delay Effect..."
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;info "by Roger Dannenberg, modified by David R. Sky\nReleased under terms of the GNU General Public License Version 2 \nDelay type: 'bouncing ball' makes the echoes occur increasingly close\ntogether (faster); 'reverse bouncing ball' makes them occur increasingly far\napart (slower). In either bouncing ball effect, delay time is not time between\nechoes but the * maximum * delay time in bounces.\nApplying delay can cause clipping (distortion), especially when reducing the\ndecay value and using more echoes. It's normally best to use Effect > Amplify\nto set the peak amplitude to -6 dB before using delay.
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;action "Applying Delay Effect..."
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;info "by Steve Daulton. Based on an effect by David R. Sky.\nReleased under GPL v2.\n"
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;; by Steve Daulton, July 2012.
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;; based on 'Delay' by David R. Sky
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;; Released under terms of the GNU General Public License version 2:
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;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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;;
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;; For information about writing and modifying Nyquist plug-ins:
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;; http://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
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;control delay-type "Delay type" choice "regular,bouncing ball,reverse bouncing ball" 0
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;control decay "Decay amount [dB; negative value increases volume]" real "" 6 -1 24
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;control delay "Delay time [seconds]" real "" 0.5 0 5
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;control shift "Pitch change per echo [semitones; negative value = lower, 0 is off]" real "" 0 -2 2
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;control count "Number of echoes" int "" 5 1 30
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; Delay by Roger B. Dannenberg
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; modified by David R. Sky October 2007,
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; adding negative decay values, which gives delay effect
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; increasing volume with each delay; and adding
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; bouncing ball and reverse bouncing ball delay effects
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; and pitch [semitone] change with each echo.
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; modified by Richard Ash January 2008, removing all
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; normalization functions.
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; Note by Roger Dannenberg: this effect will use up memory proportional to
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; delay * count, since that many samples must be buffered
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; before the first block is freed.
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; initialize empty error message
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(setf error-msg "")
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;control dgain "Delay level per echo (dB)" real "" -6 -30 1
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;control delay "Delay time (seconds)" real "" 0.3 0 5
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;control pitch-type "Pitch change effect" choice "Pitch/Tempo,LQ Pitch Shift" 0
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;control shift "Pitch change per echo (semitones)" real "" 0 -2 2
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;control number "Number of echoes" int "" 5 1 30
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;control constrain "Allow duration to change" choice "Yes,No" 0
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; check function: returns 1 on error
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(defun check (arg min max)
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(if (and (>= arg min) (<= arg max))
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0 1))
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;; The default pitch shift effect is a simple resampling,
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;; so both pitch and tempo of the delayed audio will change
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;; [as in Audacity's Change Speed effect].
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;; LQ Pitch Shift (Low Quality) changes the pitch without
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;; changing the tempo, but the sound quality is not very good
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;; and tends to cause a short echo effect which can be quite
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;; noticeable on percussive sounds though may be acceptable
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;; on other sounds.
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(setf err "") ; initialise error message
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(defun err-chk (arg min max)
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(if (or (< arg min) (> arg max))
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T nil))
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(when (err-chk number 1 50)(setq err (format nil
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"Number of echoes '~a' outside valid range 1 to 50.~%~a"
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number err)))
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(when (err-chk shift -12 12)(setq err (format nil
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"Pitch change '~a' outside valid range -12 to +12 semitones.~%~a"
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shift err)))
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(when (err-chk delay 0 10)(setq err (format nil
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"Delay time '~a' outside valid range 0 to 10 seconds.~%~a"
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delay err)))
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(when (err-chk dgain -30 6)(setq err (format nil
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"Delay level '~a' outside valid range -30 to +6 dB.~%~a"
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dgain err)))
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; checking for erroneous user-input values:
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(setf error-msg (if (= (check decay -1 24) 0)
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error-msg
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(strcat error-msg
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(format nil "Decay value '~a' outside valid range -1.0 to 24.0 dB.
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" decay))))
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(setf error-msg (if (= (check delay 0 5) 0)
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error-msg
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(strcat error-msg
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(format nil "Delay value '~a' outside valid range 0.0 to 5.0 seconds.
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" delay))))
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(setf error-msg (if (= (check shift -2 2) 0)
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error-msg
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(strcat error-msg
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(format nil "Pitch change value '~a' outside valid range -2.0 to 2.0 semitones.
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" shift))))
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(setf error-msg (if (= (check count 1 30) 0)
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error-msg
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(strcat error-msg
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(format nil "Number of echoes '~a' outside valid range 1 to 30 echoes.
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" count))))
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; finished error-checking
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; if error-msg is longer than 0 characters,
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; prepend opening message
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(setf error-msg (if (> (length error-msg) 0)
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(strcat "Error -\n\nYou have input at least one invalid value:
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" error-msg)
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error-msg))
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(cond ; 1
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((> (length error-msg) 0)
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(format nil "~a" error-msg))
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(t ; no input errors, perform delay
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; convert shift value to a value the Nyquist code understands
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(setf shift (expt 0.5 (/ shift 12.0)))
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; for bouncing ball effects, set delay time to delay time/count
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(setf delay (if (> delay-type 0)
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(/ delay count) delay))
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;;; anti-alias low pass filter
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(defun lp-wall (sig freq)
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(do ((count 0 (1+ count))
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(freq (* 0.94 freq)))
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((= count 10) sig)
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(setf sig (lowpass8 sig freq))))
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; function to stretch audio
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(defun change (sound shift)
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(if (arrayp sound)
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(vector
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(force-srate 44100 (stretch-abs shift (sound (aref sound 0))))
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(force-srate 44100 (stretch-abs shift (sound (aref sound 1)))))
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(force-srate 44100 (stretch-abs shift (sound sound)))))
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;;; Change speed
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(defun change-speed (sig shift)
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(if (= shift 0) ; no pitch shift
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sig
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(let ((ratio (expt 0.5 (/ shift 12.0)))) ; shift value as frequency ratio
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(force-srate *sound-srate*
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(stretch-abs ratio (sound sig))))))
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(cond ; 2
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((= delay-type 0) ; regular delay
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; delay function
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(defun delays (s decay delay count shift)
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(if (= count 0) (cue s)
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(sim (cue s)
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(loud decay (at delay (delays (change s shift)
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decay delay (- count 1) shift))))))
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;;; pitch shift audio
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(defun p-shift (sig shift)
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(if (= shift 0) ; no pitch shift
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sig
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(let ((sig (force-srate 44100 sig)) ; pitshift quality best at 44100
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; anti-alias filter frequency
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(minrate (* 0.5 (min *sound-srate* 44100)))
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(ratio (expt 0.5 (/ shift -12.0)))) ; shift value as frequency ratio
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(force-srate *sound-srate* ; convert back to correct rate
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(progv '(*sound-srate*) (list 44100) ; pitshift requires rates to match
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(cond
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((> shift 5) ; reduce aliasing
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(pitshift (lp-wall sig (/ minrate ratio)) ratio 1))
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((< shift -2)
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(pitshift (hp sig 20) ratio 1)) ; reduce sub-sonic frequencies
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(T (pitshift sig ratio 1))))))))
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(stretch-abs 1 (delays s (- 0 decay) delay count shift)))
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;;; apply effects to echo
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(defun modify (sig num gain shift p-type)
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(let ((gain (db-to-linear (* num gain)))
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(shift (* num shift)))
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(if (= p-type 0)
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(mult gain (change-speed sig shift))
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(mult gain (p-shift sig shift)))))
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;;; compute echoes
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(defun delays (sound gain delay shift num type mod)
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(let ((echo (s-rest 0)))
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(do ((count 1 (1+ count))
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(dly 0))
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((> count num)(sim echo sound))
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(setq dly
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(case type
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(0 (+ dly delay))
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(1 (+ dly (* delay (- (1+ num) count))))
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(2 (+ dly (* delay count)))))
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(setf echo (sim
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(at 0 (cue echo))
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(at-abs dly
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(cue (modify sound count gain shift mod))))))))
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((= delay-type 1) ; bouncing ball delay
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; bouncing ball delay function
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(defun bounces (s decay delay count shift)
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(if (= count 0) (cue s)
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(sim (cue s)
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(loud decay (at (mult delay count)
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(bounces (change s shift) decay delay
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(- count 1) shift))))))
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(defun constrain-abs (sig dur)
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(extract-abs 0 dur (cue sig)))
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(stretch-abs 1 (bounces s (- 0 decay) delay count shift)))
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((= delay-type 2) ; reverse bouncing ball delay
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; reverse bouncing ball delay function
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(defun revbounces (s decay delay count revcount shift)
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(if (= count 0) (cue s)
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(sim (cue s)
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(loud decay (at (mult delay (- revcount count))
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(revbounces (change s shift) decay delay
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(- count 1 ) revcount shift))))))
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(setf revcount (1+ count))
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(stretch-abs 1 (revbounces s (- 0 decay) delay count revcount shift)))
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) ; end cond2, different delay effect choices
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) ; end cond1 t
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) ; end cond 1
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;;; return errors or process
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(if (> (length err) 0)
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(format nil "Error.~%~a" err) ; return error
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(let* ((delay (if (= delay-type 0) delay (/ delay number)))
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(output
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(multichan-expand #'delays
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s dgain delay shift number delay-type pitch-type)))
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(if (= constrain 1)
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(multichan-expand #'constrain-abs output (get-duration 1))
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output)))
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