Bay Area rapper and producer Iamsu! is at the forefront of California's recent so-called ratchet music wave -- fun, minimal, horny, utterly unserious dance-rap that's reliably some of the catchiest non-Taylor Swift stuff on the radio these days. Next month, he'll release his new solo mixtape $uzy 6 $peed; download the deliriously infectious first single "Mobbin'" below. Iamsu! - "Mobbin'" ...