I have a tin ear. I can't play any instrument, and when I sing the milk turns sour. That's why I play a minstrel in LotRO, because when *he* sings, wolves drop dead. :) But a lot of other people are a lot more musical than me. And Lord of the Rings Online gives them the opportunity to prove it, with the /music command. If you have the appropriate character skill, which all classes get at level 5, only the guardian needs to wait to level 10, and you equip an instrument, you can turn music mode on by typing the /music command. Then you can play notes on your instrument, for everybody around you to hear. And that's all I know about the subject. I tried it, the harp I equipped turned out to have the graphics of a flute, and I still can't hold a tune. So if you want more information, check out the info on DMOsbon's blog.
Oh, and you might want to invest in a programmable keyboard or something, because there isn't any way to record a tune and play it back yet, only live performances in this game right now. Rumor has it the next content patch will improve that.