Fixed bug that caused all tracks to play to channel 1. Thus all track…

[cwurld]

…s were played with the instrument in track 1.

Fixed bug that caused note outside of track one to never stop. All stop commands were being sent to channel 1.

Added an example that was affected by these bugs and now plays correctly.

[yansnow78]

there is he same bug with property velocity. I don't understand how this bug can be there since 2 years without any correction

an other way to fix it is to replace the following line in Sequencer.play_Note(...) #96

    if hasattr(note, "velocity"):
        velocity = note.velocity
    if hasattr(note, "channel"):
        channel = note.channel

by

    if "velocity" in note.__dict__:
        velocity = note.velocity
    if "channel" in note.__dict__:
        channel = note.channel