Late last week, Twitter continued its push into the mobile-app space with Twitter #Music, a free iPhone\/iPod touch app for sampling and sharing popular music. If you\u2019re interested in discovering what\u2019s trending musically in the Twitterverse, it doesn\u2019t get any easier\u2014or more entertaining\u2014than this.\n\tTwitter #Music has a slick interface. A \u201cPopular\u201d chart lets you view the 140 most popular songs on Twitter. (The 140 number is appropriate given Twitter\u2019s famous 140-character count limit.) You can tap a track\u2019s thumbnail to listen to its iTunes 30-second preview. If you have a premium Spotify or free Rdio account, you can link them to Twitter #Music and listen to the full tracks.\n\tAs a song plays in Twitter #Music, a virtual "turntable" spins in the bottom left corner, and an audio-level meter pulses up and down. If you tap the rotating turntable a secondary screen pops up, which can be used to adjust the volume with a slider bar, send audio to an Apple TV or Apple Airport Express, or tweet the track you\u2019re jamming to via a Twitter button. And Twitter icons within tracks' thumbnail images let you quickly follow artists.\u00a0\n\tIn addition to the "Popular" chart, the app has an "Emerging" chart of up-and-coming musicians; a "Suggested" chart, with recommendations based on songs you\u2019ve tweeted and artists you follow; and "Now Playing," with songs tweeted by people you follow. A drop-down menu at the top of the screen lets you navigate between charts. Or you can just swipe between them.\n\tI had a lot of fun using Twitter #Music, but I do have a few small gripes. The music that's available for sampling tends to be of-the-moment, rather than classics by, say, The Beatles. In that sense, Twitter #Music is a narrower option for discovering music you might like but haven\u2019t heard before, compared to a service like Pandora.\n\tIf you connect the app to Rdio or Spotify, iTunes is no longer the default listening choice. That\u2019s fine if you want to hear the entire track in Twitter #Music. But if you want to buy the track for offline listening, you need to leave Twitter #Music and search for it in the iTunes app. If you keep iTunes as your default playing option, an iTunes icon in Twitter #Music takes you to that track in the iTunes app, where you can buy it.\n\tAlso, for the moment at least, Twitter #Music is only available for iOS. Small quibbles aside, if you want to stay current with music, or just give your kids the impression you\u2019re cool, you'll find a friend in Twitter #Music.