helper:arpeggio   scheme

;
;
;; inner function for :arp
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; eg 
; (helper:arpeggio (*metro* 'get-beat) 0 
;   '(c4 f4 g4 c5) 3 90 3) ;; durs/vols do not need to be a list
; (helper:arpeggio (*metro* 'get-beat) 0
;   '(c4 f4 g4 c5) '(3) '(90) 3) ;; a list works too
(define helper:arpeggio
  (lambda (beat offset notes durations volumes ch)
    (let* ((durs (cl:expand-list2 durations (len notes)))
          (vols (cl:expand-list2 volumes (len notes)))
          (total_dur (sum_list durs))
          (wait (car durs)))
      (when #f (println notes durs))
      (play (eval offset) ch (eval (car notes)) (car vols) total_dur )
      (if (not (null? (cdr notes)))
        (callback (*metro* (+ beat (* 1/2 wait))) 
          'helper:arpeggio (+ beat wait) offset
          (rest notes) (rest durs) (rest vols) ch)))))