helper:playchord   scheme

;
;
;; HELPER:PLAYCHORD 
;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Inner function used by PLAY: midi-play multiple notes at the same time 
;
; Args:
;; 1st: beat
;; 2nd: offset, atom or list
;; 3rd: channel, 1-based
;; 4th: pitch-list
;; 5th: velocity/vol, atom or list
;; 6th: dur, atom or list
;
;
; (let ((beat (*metro* 'get-beat))) 
;   (helper:playchord beat 0 piano 
;     (list c4 g4) 
;     (:mklist 2 (random 10 90)) 
;     (:mklist 2 (oneof 1 2 3)) )
;   )
;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define helper:playchord
  (lambda (beat offset_or_list ch plist vol_or_list dur_or_list)
    (when #f (monitor  beat offset_or_list ch plist vol_or_list dur_or_list))
    ;; make lists for vols and durs, if atoms are passed
    (if (atom? offset_or_list)
      (set! offset_or_list (list offset_or_list))) 
    (if (atom? vol_or_list)
      (set! vol_or_list (list vol_or_list))) 
    (if (atom? dur_or_list)
      (set! dur_or_list (list dur_or_list))) 
    ; volumes & durs: ensure it's the right length
    (let (
            (offsets 
              (cl:expand-list offset_or_list (- (length plist) (length offset_or_list)))) 
            (volumes (cl:expand-list vol_or_list (- (length plist) (length vol_or_list))))
            (durs (cl:expand-list dur_or_list (- (length plist) (length dur_or_list)))) 
          ) 
          (when #f (monitor  volumes durs))
          (for-each (lambda (o p v d)
                      (play-midi-note (*metro* (+ beat o)) *mididevice*
                                        (helper:midi-val (eval p))
                                        (helper:midi-val (eval v))
                                        (*metro* 'dur (* *play-midi-default-dur-factor* d)) 
                                        ;; NOTE ch is 0based in xtm, but user sends it as 1-based
                                        (- ch 1)
                                        ))
                        offsets plist volumes durs)
                    ) 
    ) 
)