It became apparent during the hsc, prelim whatever that unless I listened to music I probably wouldn't get much done since I needed something to get me interested in something so I wouldn't be quite as bored when it came to studying. Then it was useful for microbreaks, a minute or so where I wouldn't study then I get back into it with the next song. Usually kept the volume on almost medium. I don't really listen to music loudly, unlike most people. I listened to all sorts of music. Anberlin, Basshunter, video game/show soundtracks, dc talk, evanescence, paparizou, hillsong, Lecrae... could go on and on but you get the idea.
That said, youtube probably stripped me of 2 ATAR points lol since I spent ages developing a playlist then spent ages doing anything on youtube haha. This was BEFORE I had fb as well, though I also had msn. EDIT: Ok 2 is a bit of an exaggeration, but I wouldn't have had it any other way anyway. Schoolwork was boring!
There were some times eg ext1 maths where I was listening to the music at first then after a while I really tried to work around the q and the music got in the way. So I just turned it down to close to all the way.