Der Brucer and I saw Bart in a show he did earlier than YAGMCB. He was in Triumph of Love on Broadway, along with such unknowns as Susan Egan, Kevin Chamberlin, Nancy Opel, Christopher Seiber, Betty Buckley, and the most fabulous singer you'll ever hear, F. Murray Abraham.
Yet another show that didn't really work on Broadway, but works very well in regional theater, IMO.
In another Bart/Egan pairing, he did the singing for young Hercules and Susan sang/voiced Meg in the Disney animated film a few years back.