Playing sounds using either the player.playNote(); or world.playNote(); methods send their sound packets with an empty source data. This causes the client to play the notes to the default channel (Music) while there is a slider available for Noteblocks and Jukebox sounds.

Steps to reproduce:
1. Turn down music volume slider.
2. Place and activate a noteblock. a sound will be heard.
3. send a note to the player using the bukkit methods. No sounds can be heard.
4. Turn up the music volume slider.
5. Send a note to the client again. This time the note should play normally.

Suggested fix:
Add the Sound Catagory to the packet that gets send after triggering player/world.playNote();