Sometimes life's so bad you can't even play the blues. Junior, a down-on-his-luck trumpet player from the Bronx who's struggling with a fraught past and a nasty case of creative block, turns to his Muse for help. But she has none left to give (a red flag if ever there was one) and she has to beg Lorca to lend her his duende. In the ensuing dialogue between Junior and his Muse, playwright-performers Steven Sapp and Mildred Ruiz explore the fickle natureas well as the limitsof inspiration and creativity. Mostly, they dwell on the limits. Still, it would be uncharitable to dismiss their musical Eyewitness Blues as uninspired. Riffing on sources as disparate as jazz, hip-hop, flamenco, poetry slam, Spanglish, and the daytime talk show confessional, they hit at least as many high notes as low ones. But Sapp's monologues tend to meander aimlessly like overextended improv solos, without ever thoroughly fleshing out his character. In the end, the one-act feels less like a fully developed evening of theater than like an impromptu jam session with first-rate artists: two talented, charismatic actors who deserve better material than their own. Ruiz, in particular, has a larger-than-life stage presence and a voice to match, far too big for the New York Theatre Workshop's intimate house.