Kaba class SongRenderer ed

class SongRenderer extends AudioSource
    var name: string
    var out_changed: source
    var out_play_end_of_stream: source
    var out_read_end_of_stream: source
    var out_state_changed: source
    var out_tick: source
    var output: OutPort
    var port_out: OutPort&[]
    var session: Session&

    # constructors
    func mut __init__(s: Song)

    # functions
    func selfref get_beat_source() -> BeatSource*
    func get_pos() -> i32
    func range() -> Range
    func mut virtual read(out b: AudioBuffer) -> i32
    func mut render(r: Range, out buf: AudioBuffer)
    func mut set_loop(l: bool)
    func mut set_pos(pos: i32)
    func mut set_range(r: Range)