From the developer:
  “To make it automatically scroll the lyrics, you have to sync them one time yourself. That means tapping the album art to advance the lyrics all the way through the song. At that point the timing information is sent back to our servers and stored. Next time someone requests lyrics for that song they will get it with your timing already there.If you get a synced set of lyrics that are all messed up you can hit the “resync” button and redo it. It’s all community maintained (which is why it’s called Tune”wiki”)BTW the lyrics are stored locally for any song you’ve gotten already. That way if you’re out of the service area you’ll still have them.”