These buskers have brains. Lots and lots of brains. Guitarist and singer Khalil Sullivan is a graduate student in English at UC Berkeley, and he's using his experience with the motley crew of musicians he has assembled in Mad Noise — which include an upright bass player, a harmonica whiz, and a dude who will turn anything into a drum — to prepare for his thesis. The subjects? Music, race, the recording industry. On Saturday nights you can often find Mad Noise thumping on various corners in the Mission District, playing its mix of covers and originals — and that's usually after the group has played for hours in its home base of Berkeley. The music can be chaotic and entrancing (and sometimes downright messy), but it's always charismatic, led by Sullivan's winsome voice. And as you'd expect from a band led by a guy who performed for Toni Morrison at Princeton, there's much more to Mad Noise than "Can you spare any change?" Although the band wouldn't turn that down, either.