Take a Big Ten marching band, add a pinch of Riverdance, a dash of Stomp, and a heap of Debbie Allen-style interpretive dance. Cram it onto a stage, pump up the volume, and you’ve got a spectacle that’s more of a dud than a blast. Blast! has the trappings of a crowd-pleaser: flashy lighting; rousing music from the likes of Ravel and Copland; and a young, eager cast of 60 whose smiles sparkle like their well-polished trumpets. All this business seems tailor-made for the football field but misplaced on Broadway.