Sonic Rush Adventure (DS)

Muzy (Sound Test)
After defeating the Titan boss in Big Swell, go to Seagull Beach on Windmill Island and talk to the koala with the guitar. You will now be able to listen to music, sound effects and dialogue from the game, and can receive missions which unlock extra sounds once completed.

Play as Blaze
Defeat the Kraken Boss in World 3 (Coral Cave) to play as Blaze the cat.

Sound test
Defeat the Titan Boss in Big Swell. Then go to Seagull Beach on Windmill Island. Talk to the koala with the guitar to hear the music, dialogue, and sound effects. This will also open additional missions.