Jason Robert Brown's time-traveling musical The Last Five Yearsis sustained by two characters and sixteen songs in one act. Sounds like an ideal show for the St. Louis Rep Studio -- and it was. Under the direction of John Ruocco, this dissection of the life and death of a marriage was perfectly calibrated for the intimate studio space. Best of all, it did not attempt to replicate the 2002 off-Broadway production. (Not that most audience members would have known; the New York production didn't run all that long.) In a musical that demands a lot of thought from the audience, this intricate Rep production gave us a lot to think about. Credit, too, actors Anthony Holds and especially the engaging Kate Baldwin for carrying off a unique and fascinating theater experiment.