(define pitch-list (list 60 61 63 67 64 66 70 69 72))
(define rhythm-list (list 1.5 1.125 1.375 1.0 1.625 1.875 2.0))
(define dynamics-list (list 0 0.75 1.0 0.33 0.66))

(define (make-note start pitch length dynamic voice)
  (new midi
    :time start
    :keynum pitch
    :duration length
    :amplitude dynamic
    :channel voice))

(define (rotate-left input-list)
  (append (cdr input-list)
          (list (car input-list))))

(define (make-isorhythm notes start pitches durations dynamics voice)
  (if (<= notes 0)
    nil
    (cons (make-note start (car pitches) (car durations) (car dynamics) voice)
          (make-isorhythm (- notes 1) 
                          (+ start (car durations))
                          (rotate-left pitches)
                          (rotate-left durations)
                          (rotate-left dynamics)
                          voice))))

(define (transpose transposition pitch-list)
  (if (null? pitch-list) 
    nil
    (cons (+ transposition (car pitch-list))
          (transpose transposition (cdr pitch-list)))))

(define (make-canon transpositions entrances voices notes start pitches durations dynamics)
  (if (or (null? transpositions)
          (null? entrances))
    nil
    (let ((current-pitches (transpose (car transpositions) pitches)))
      (append (make-isorhythm notes (+ start (car entrances)) current-pitches durations dynamics (car voices))
              (make-canon (cdr transpositions)
                          (cdr entrances)
                          (rotate-left voices)
                          notes start pitches durations dynamics)))))

(define (prolate scale duration-list)
  (if (null? duration-list)
    nil
    (cons (* scale (car duration-list))
          (prolate scale (cdr duration-list)))))

(define (make-prolation-canon transpositions entrances prolations voices notes start pitches durations dynamics)
  (if (or (null? transpositions)
          (null? entrances)
          (null? prolations))
    nil
    (let ((current-pitches (transpose (car transpositions) pitches))
          (current-rhythms (prolate (car prolations) durations)))
      (append (make-isorhythm notes (+ start (car entrances))
                              current-pitches current-rhythms dynamics (car voices))
              (make-prolation-canon (cdr transpositions) (cdr entrances) (cdr prolations)
                                    (rotate-left voices) notes start pitches durations dynamics)))))