Presumably it's the written music for if you wanted to perform it yourself, rather than being something you can actually listen to. Unless you're a musician I wouldn't worry!

sheet music is basically the notes and words of a particular piece of music, so that you can play it yourself. like if you go to see an orchestra, the musicians are looking at sheet music as they play. Blizz apparently released Lament of the Highborne as sheet music so you could play it on the piano or guitar or whatever.

Sheet music is the written staff, notes, measures, timing, clef and notation of a given piece of music (gee, that almost made me sound smart!) - here's an example:

http://ursispaltenstein.ch/blog/images/uploads_img/classical_music_sheet.jpg

That's sheet music? Kick ass, couldn't figure out what it was. Thought it was a record, for a minute...

"Wondering if I need it or not".

I found this kinda cute. He needed to know what it was...to know if he needed it or not. :-)

The highborne sheet music said it was sold at one minute, and then later that it was not. Also, initially, there were 63 items, and then within about 15 minutes i noticed it became 73. Something to be aware of, keep checking the sales page.

You best be troll'in...oh wait... you're serious. -_-;

who else is shocked that it sold out so fast!