Rock the Bells, a cinema verite-style ride through the production, promotion, and potential implosion of the 2004 hip hop concert of the same name, is starting to gather buzz at Tribeca as "the doc that spends 40 minutes trying to get a cracked-out Ol' Dirty Bastard out of his hotel." It is that film, for sure, but it's also at least three other things. It's a crash course in the dirty business of concert promotion; it's a primer on the storied history of Wu Tang Clan, who are not only one of the most significant hip hop acts, in creative terms, of all time, but are also responsible for taking the art of branding to a whole new level; and it's a love letter to fans and fandom that is so heartfelt, it bleeds through the boundaries of musical taste. Still, it would be hard to overstate the suspense that the Dirty situation lends to the film (which, at two hours, is slightly overlong but not fatally so). Directors Denis Henry Hennellyand Casey Suchan have themselves a poster-ready tagline in the film's first 15 minutes, when Chang, the concert promoter at the film's center, tells his assistant, "Anything with Dirty makes me nervous."