Everyone must start somewhere, and for Fred Lassen, South Pacific's musical conductor, that somewhere was the fourth national bus-and-truck tour ofCats. That's not really true: previously, there was a degree in organ performance from Oberlin, and a summer as a rehearsal pianist at the now-defunct Candlewood Playhouse in Connecticut, and, before everything, some parental prodding. "I grew up near Rochester, New York, and I started piano lessons at 12," Lassen said the other evening in his dressing room. "I kicked and screamed, but my mom forced me."

Discussing a bus-and-truck tour of Cats, however, brings out one of Lassen's signature qualities: generosity. He doesn't complain about the tour's rigors - the constant moving around, the staccato pace of life in places in which one might never choose to vacation. Instead, Lassen talks about the tour's geographical variety: Cats gave me a chance to see the country. I'm a runner, and in almost every city - except places like Houston, which are all roads and freeways - I made sure I didn't stay glued to the hotel. I got out."

In the world of LCT's South Pacific, Lassen's generosity extends not just to his conducting, where every night he strives to support the singers, to lead the musicians ("a really great group," he emphasizes), and to shape the orchestral sound with the expressivity of his gestures. His expansiveness also involves extracurricular activity. When some of the cast sang the National Anthem recently at a Mets Game, Lassen helped with the vocal arrangement. When some of the same guys plus Danny Burstein performed on Memorial Day as part of New York's Fleet Week activities, Lassen was there, too. And when Paulo Szot needed a musical director for his concert this past winter in Lincoln Center's American Songbook series, again it was Lassen.

Such team spirit may be innate to his temperament; it is also a reflection of his appreciation for the South Pacific gig. "It's so rare," Lassen says -- who on Broadway has also conducted Cabaret, 42nd Street, and Dirty Rotten Scoundrels -- "to be able to conduct a score these days where you are essentially using the original orchestrations. Most shows now are re-orchestrated for much smaller ensembles." He added: "Some shows you could just set a metronome up in front of the players, instead of a conductor, and they would do just as well. Not in South Pacific."

Even with all the pleasures of the job, doesn't Lassen ever get bored, even just a little? "No," he replies. "With music like this, with singers and orchestra players like this, you have to be in the moment for every performance. You can't afford to be bored."

BRENDAN LEMON is the American theater critic for the Financial Timesand the editor of lemonwade.com.