as_part_midi.xtm

;;; as_part_midi.xtm -- live performance
;; based on Andrew Sorensen  "A Study in Pärt" Impromptu performance
;; A study in simplicity - a study in Pärt.
;; Based on Arvo Pärt 'Cantus in Memory of Benjamin Britten'
;; https://vimeo.com/2434054
;; 
;; Orginal code translated to Extempore
;; http://extempore.moso.com.au
;;
;; Author: cv
;; Keywords: extempore, live-coding, impromptu, arvo pärt
;;; Commentary:

;;; Code:

;; load MIDI library

(sys:load "libs/external/rtmidi.xtm")

;; midi stuff
(define *midi-out* (midi_new_outdevice))

;; query for valid midi output devices
(midi_query_outports *midi-out*)

;; now open output port (assuming port 0)
(midi_open_outport *midi-out* 0)

;; play midi test note

(play-midi-note (now) *midi-out* 72 20 10000 0)


;; requires pc_ivl-lib  Pitch Class Library

(sys:load "libs/core/pc_ivl.xtm")


;; set tempo

(*metro* 'set-tempo 80)

;; define scale
(define scale (pc:scale 0 'aeolian))

(define volume 1)
;; performance starts here


(define arvo
  (lambda (time start pitch dur channel)

     (play-midi-note (*metro* time) *midi-out* pitch
          (real->integer volume)
          (*metro* 'dur dur) channel)
     (set! volume (+ volume 1)) (println volume)

    (callback (*metro* (+ time (* 0.5 dur))) 'arvo (+ time dur)
               (if (> pitch (- start 12))
                  start
                  (pc:relative start -1 scale))
               (if (> pitch (- start 12))
                  (pc:relative pitch -1 scale)
                  start)
               (random '(3 2 1))
               channel)))


;; start playing violin ensemble part
(arvo (*metro* 'get-beat 4) 96 96 3 0) 
;; add second violin part
(arvo (*metro* 'get-beat 4) 84 84 3 0) 
;; add viola ensemble
(arvo (*metro* 'get-beat 4) 72 72 3 1) 
;; add cello ensemble
(arvo (*metro* 'get-beat 4) 60 60 3 2) 

;; changes to arvo code
;; decrease volume (set! volume (- volume 1)) (println volume)
;; change durations
;;     (set! volume (- volume 1)) (println volume)
;;               (random '(3 2 4))


(define arvo
  (lambda (time start pitch dur channel)

     (play-midi-note (*metro* time) *midi-out* pitch
          (real->integer volume)
          (*metro* 'dur dur) channel)
     (set! volume (- volume 1)) (println volume)

    (callback (*metro* (+ time (* 0.5 dur))) 'arvo (+ time dur)
               (if (> pitch (- start 12))
                  start
                  (pc:relative start -1 scale))
               (if (> pitch (- start 12))
                  (pc:relative pitch -1 scale)
                  start)
               (random '(3 2 4))
               channel)))


;; change durations
;;               (random '(3 2 6 4))
;; change durations
;;               (random '(3 6 4))
;; change durations
;;               (random '(6 5 4))
;; decrease volume (set! volume (- volume 0.5)) (println volume)
;; decrease volume (set! volume (- volume 0.25)) (println volume)
;; stop decrease volume (set! volume (- volume 0)) (println volume)
;; change durations
 ;; change durations
;;               (random '(6 5 8))
;; decrease volume (set! volume (- volume 0.25)) (println volume)
;; change durations
;;               (random '(6 7 8))
;; change durations
;;               (random '(6 12 8))
;; decrease volume (set! volume (- volume 0.125)) (println volume)
;; stop decrease volume (set! volume (- volume 0)) (println volume)

;; stop recursion
(define arvo)

;; the end