In Sonic Adventure 2:Battle, each character has a theme song. I played the hero side, got to Eggman sending the Egg Golem after Sonic, and when that happened, I heard lyrics from Eggman's theme that weren't on the song in the sound test. This has also ocurred with Knuckles and Rouge. Is there a way to unlock the full versions?
The full songs aren't available in Sound Test, and you can't unlock them. Occasionally, however, the full song will play in certain cutscenes. If you want the full versions, you can buy the soundtrack online.

~ Crazy C Lea