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; Triangle wave with a period of 1 second
(define (tri t)
(let ((m (floor-remainder (+ t (/ 1 4)) 1)))
(if (< m 1/2)
(- (* 4 m) 1)
(- 3 (* 4 m)))))
; Square wave with a period of 1 second
(define (square t)
(let ((m (floor-remainder t 1)))
(if (< m 0.5) 1 -1)))
; Creates a note
(define (note freq start len)
(lambda (t) (
if (or (< t start) (>= t (+ start len)))
0
(* 1/4 (tri (* 1.5 t freq))))))
;
; Gets the frequency of a particular pitch
(define (getfreq octave pitch)
(* 55 (ash 1 octave) (expt 2 (/ pitch 12))))
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