The service uses information from Twitter chatter to detect popular tracks as well as new artists. Users who follow musicians can see other artists those musicians follow and can listen to 30-second clips of songs by them.
While users can tweet what they're listening to and add a few characters of comment, they have to go back to the regular Twitter app for normal Twitter functions. However, the people you're following and who's following you are integrated across both apps.
The service is only available in the U.S., Canada, the U.K., Ireland, Australia and New Zealand.
You can download Twitter #music from the App Store today, or enjoy the web version, here music.twitter.com