Few musicals have led off with a more bracing musical sequence than the spectacular freeway-traffic-jam-dance “Another Day of Sun,” shot on the same express-lane ramp used in the movie Speed. The song is delightful, Mandy Moore’s choreography is endlessly inventive, and the sheer amount of energy at play is quite remarkable. All praise, then, to the planning and coordination that put it all up on the screen, since Damien Chazelle and the cast and crew did the whole thing in an extraordinary two days.