A Little Night Music comes to the concert stage with the Orchestra of St. Luke’s, 53 players strong, doubling the 27 heard in the pit band of the original Broadway production three decades ago. For the occasion, Stephen Sondheim’s lifelong orchestrator Jonathan Tunick has started over from scratch, and the results should be revelatory. Sondheim called Tunick “the best orchestrator in the history of the theater,” though not, perhaps for the reason you’d first suspect. “There are many who are as skilled at putting instruments together,” Sondheim continued, “but not any who have the sense of theater that he has.” Tunick himself conducts a hand-picked cast led by Ron Raines and the glamorous operatic mezzo Susan Graham as the once and future lovers Fredrik and Désirée, alongside Shuler Hensley and Ruthie Ann Miles as the self-lacerating Count Carl Magnus and Countess Charlotte. In a stroke of especially luxurious casting, Cynthia Erivo plays the maid Petra, who gets a few sassy lines of dialogue and the song “The Miller’s Son,” one of the handful of songs the notoriously self-critical composer conceded “came out right.” —Matthew Gurewitsch