It was 9:45 p.m. on Santa Monica Boulevard when New York-based Cymbals Eat Guitars begins to play at the Troubadour on Sept. 19. Joseph D’Agostino, 20, fronts the band, putting on what he claims to be their best performance. The venue is old with eroding concrete walls. The staircase leading to a bands only lounge can scarcely hold itself up. Even so, this doesn’t seem to take away from their energy.