We have to thank the ESRB website for dishing out more specific details on game content. From the ESRB website, we learn a little more about the PSP's upcoming Rock Band Unplugged. There's a brief mention of the inclusion of guitar, bass and drums in the game. There's also four songs that can be confirmed for Rock Band Unplugged, based on the ESRB descriptions.
From the ESRB ratings info, these tracks will be in Rock Band Unplugged:
"What's My Age Again?" by Blink 182
"Lump" by The Presidents Of The USA
"My Own Worst Enemy" by Lit
"Chop Suey" by System of a Down
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