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.
Tapping the play button on an image of an artist plays a clip from one song picked to represent them. Users can tap another button that opens iTunes, where they can buy the track. Or they can play full songs by signing up for a $10-a-month subscription from Spotify or Rdio.
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.
In a blog post, the company said its service "will change the way people find music." It is calling the app #music, following its practice of using hashtags to organize tweets around topics.