If you’re someone who has to have music to study to, preparing playlists can take up more time than the actual learning. Particularly if you want to have control over what kind of music you’re listening to, most music services require a great deal of fine-tuning.
Pandora, though excellent if you don’t need to focus, builds playlists on artist characteristics rather than moods. Because it’s curated automatically, it can sometimes wildly miss the mark–tossing up “Boy Named Sue” when you want unintrusive music for other activities.* Grooveshark‘s great, and its selection can’t be beat, but it requires time-consuming curation. It’s a fabulous option if you want control over a party playlist, but it’s too time-intensive for study background music–the same issue as iTunes playlists, which have the added downside of being confined to music you actually own. And, though Frat Music crosses over most of these issues, it isn’t quite what you want to study to.