Tedium, tunelessness, embarrassment even the best open mics in town can't avoid valleys of musical despair. Blame it on the form or on out-sourced, mass-produced acoustic guitars. But Café Soul, the once-a-month throwdown at the Lucas School House, offers more peaks than pits, more groove than grunge, more panache than posturing. With a killer house band, DJ Needles on the between-sets spins and charismatic emcee Mocha Latte, the nights move fast, the performers rap and wail, and the packed house, mostly made up of African Americans between 21 and 51, only sits politely when told to do so. For the most part, they cheer on covers of Beyoncé, funky originals or political poems that put the typical open-mic navel probes in their white-bread place.