News of R&B superstar Maxwell's return after a long hiatus is a reminder of times past, and not just his previous career. For every John Legend or Brian McKnight laying down dulcet tones, a Jimmy Scott or Al Hibbler paved the way. In its latest original production, the Black Ensemble Theater looks back with the story of two generations of crooners trying to save their 60-year-old family business, a legendary nightclub. As is typical of jukebox musicals, the plot is a simple frame on which to hang the real artwork, in this case the timeless songs of Billy Eckstine, Nat "King" Cole, Roy Hamilton, Johnny Mathis, and many others. It's the most tuneful history lesson now playing.