how to play music?Follow

If you mean you want to play instruments to improve the effect of your skills and combat arts you just equip the instrument and when you use a skill the animation will display with the instrument you have equipped.

If you're talking about the recreational music system built into the game, it's a bit more complicated. A detailed description of the recreational music system can be found here:

http://forums.lotro.com/forumdisplay.php?f=108

(the link is to the music playing forum on the official site)