Preachifying moved to ThinkingMusicConsideredHarmful. Testimonials moved to GoodThinkingMusicTestimonials. Idea that music makes you smarter / plants hear music deleted because outrageously false and completely irrelevant.
I don't care whether music prevents creative thinking because I know it does. And when I get down to coding the system I've designed up, that's precisely what I want.
Requirements for non-distraction
nothing with recognizable vocals; foreign languages don't work too well because you start to pick them up
anything you're so familiar with that you've grown thoroughly sick of it
MP3 and streaming Sources that were recommended by wikizens:
http://di.fm has a whole list of channels -- chillout trance and goapsy are recommended. "progressive" works well, has occasional vocals