Complex sentence: Soundgarden frontman Chris Cornell has a cameo as the guy who comes out from he apartment block to listen to an incredibly loud car stereo, and also appears in a later scene with his band Soundgarden performing the song "Birth Ritual".
Split into simpler sentences: Soundgarden frontman Chris Cornell has a cameo as the guy who comes out to listen to a car radio. He also appears in a later scene with his band Soundgarden performing the song "Birth Ritual".