38 lines
1,007 B
Scheme
38 lines
1,007 B
Scheme
(use-modules (ice-9 binary-ports))
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; Bitrate is the number time to sample the music function each second
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(define bitrate 8000)
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; Triangle wave with a period of 1 second
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(define (tri t)
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(let ((m (floor-remainder (+ t (/ 1 4)) 1)))
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(if (< m 1/2)
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(- (* 4 m) 1)
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(- 3 (* 4 m)))))
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; Square wave with a period of 1 second
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(define (square t)
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(let ((m (floor-remainder t 1)))
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(if (< m 0.5) 1 -1)))
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; Creates a note
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(define (note freq start len)
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(lambda (t) (
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if (or (< t start) (>= t (+ start len)))
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0
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(* 1/4 (tri (* t freq))))))
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; Gets the frequency of a particular pitch
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(define (getfreq octave pitch)
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(* 55 (ash 1 octave) (expt 2 (/ pitch 12))))
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; Get the music as a list sampled at the bitrate
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(define (play t end)
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(cons ((lambda (a)
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(let ((b (modulo (inexact->exact (round (* (+ a 2) 32768))) 65536))) cons
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(put-u8 (current-output-port) (modulo b 256))
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(put-u8 (current-output-port) (quotient b 256)))) (music t))
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(if (< t end)
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(play (+ t (/ 1 bitrate)) end)
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'())))
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