The Lord of the Rings Online: Shadows of Angmar has a music system that allows you to play your own music while in the game. Characters that have reached level 5 can learn to play one or more instruments depending on their class. Instruments can be purchased from a Bard. When you put the instrument in your ranged weapons slot and use the /music command, the player will be put into music mode. You can play the instrument in real time on two octaves, using the 1-8 number keys.
An update to the music system is planned in the Shores of Evendim game update in June, 2007. This update is expected to allow players to compose music offline using a score.