root/ocaml-remix/trunk/instrument.ml

type length = float;;
type amplitude = Volume.volume;;

type soundFunction = amplitude -> Tone.tone -> Sound.sound;;
type instrument = {sound_function : soundFunction; mutable position : float};;

let from_sound_function ?(start=0.0) sf = {sound_function=sf; position=start};;

let add_note instrument layer amplitude tone length =
  Layer.add_plugin layer
                  (Plugin.from_sound (instrument.sound_function amplitude tone))
                  (Time.Beats instrument.position, Time.Beats length);
  instrument.position <- instrument.position +. length;;

let calc_length l = List.fold_right (fun (t,l) s -> l +. s) l 0.;;

let add_notes instrument layer volume notes = 
  let start_pos = instrument.position in
  let len = calc_length notes in
  let rec _add_notes notes = 
    match notes with
    | (t,l)::r -> (
        let spos = instrument.position -. start_pos in
        let epos = spos +. l in
        let s = Volume.amplitude volume spos len in
        let e = Volume.amplitude volume epos len in
        let newv = Volume.ramp s e in
        add_note instrument layer newv t l; 
        _add_notes r)
    | [] -> () in
  _add_notes notes;;