music-utilities.lisp

   1
   2 (in-package :mumble)
   3
   4 ;; 60 seconds in a minute, 4 beats per whole note.
   5 (defconstant +seconds-per-minute+ 60)
   6 (defconstant +beats-per-whole-note+ 4)
   7
   8 (defun duration-to-frames (duration tempo &optional (frequency 50))
   9   "Returns a /fractional/ duration -- the conversion routine is
  10 responsible for dealing with these fractions as it sees fit."
  11   (let ((count (/ (/ (* frequency +seconds-per-minute+)
  12                      (/ tempo +beats-per-whole-note+))
  13                   (duration-denominator duration))))
  14     ;; dots
  15     (do ((dots (duration-dots duration) (1- dots))
  16          (extra (/ count 2) (/ extra 2)))
  17         ((not (plusp dots)))
  18       (incf count extra))
  19     ;; XXX staccato, ties
  20     count))