Go for instrumental music, it doesn't activate the part of your verbal part of your brain. Essentially to hear singing (or talking) your brain mimics it, however when you're trying to read/write you've got two processes and only one processor to put it through. You can struggle through, but not nearly as well as running them solo.

Also, just go onto TPB or usenet and download some Beethoven or Wagner. It's 100% legal, no copyrights exist on them and even if they did they're so old it'd be void anyway. Even the BBC offered them up for free at some point, they were surprisingly good quality too.

I learnt this a long time ago when I was working doing reviews. When you spend 10 hours writing reviews, you need something to listen to or you're going to start shooting kids and spearing dogs for making the slightest noise.