As powerful as James Martin's amplified voice was singing "Ol' Man River" in Tulane Summer Lyric Theatre's "Show Boat" concert, sitting in the front row hearing him unmiked at a "Pippin" rehearsal was like being hit by a baritone bolt of lightning.

The company was rehearsing the show's finale ("Think about the sun, Pippin . . ."). Choreographer Diane Lala and director Ed Kresley were demonstrating some Bob Fosse-like moves and Martin was singing full out, clapping his hands, putting megavolts of energy into his slinky movement.

Martin is cast as The Leading Player, the "seductive trickster" as the actor describes him, in the Stephen Schwartz musical that opens a four-performance run Thursday at Dixon Hall, Summer Lyric's third and final show of an unexpectedly successful post-Katrina season.

The Leading Player won Ben Vereen the Tony Award in 1973 and Fosse picked up two, for best choreography and best direction of a musical.

"Fosse is breaking my body," Martin said, since Lala is using "original Fosse" in several numbers and her own take on "the Fosse style" in others.

"He made this show," she said, "and you have to pay tribute to that work, but it doesn't have to be step-for-step."

That Martin is dancing at all in a pop musical is somewhat surprising, since he is first and foremost an opera and concert singer who has performed major roles with American, Canadian and European opera companies and will concertize at Carnegie Hall next season. He also teaches voice and theater at the Juilliard School, where he received his master's degree in music.

But his credits also include significant musical theater roles.

"I think lyric theater is opera," Martin said. "The only difference between this and Mozart is that the recitative doesn't have to be sung." On occasion, he has even been able to combine Mozart and musical theater, with a New York Times review citing his "tap-dancing Papageno" (the Birdcatcher in "The Magic Flute").

"This is my summer of real delight," he said of Summer Lyric. "To be able to do 'Show Boat,' which changed musical history and brought the African-American experience and jazz onto the Broadway stage, and now this show, playing a great character who gets to do so much 'showboating,' is a treat.

"Plus, I must say that Summer Lyric parallels any company I've performed with in New York in terms of the way everyone here values the performances, the music, the production, the whole lyrical genre. I'm proud to be part of it."

Martin, whose home is in the Jackson/Camden area of Mississippi, is artist-in-residence with the Hattiesburg Civic Choral and Concert Association and a guest artist of the Mississippi Opera. He was brought to Summer Lyric director Michael Howard's attention by longtime friend and frequent Lyric performer Mildred Hong, who happens to be playing Berthe in "Pippin." Berthe is Pippin's lively grandmother, who gets to lead the buoyant audience sing-along "No Time at All."

"Michael and I have known each other since college," Hong said. "When he evacuated, he stayed with us in Hattiesburg. He was very worried about having a season this summer. Performers had scattered, everything was in an uproar, but once it was decided that the city needed Summer Lyric, he went right to work. When the decision was made to do the 'Show Boat' concert, I told him, 'There's someone I think you should hear. He sings all over the country and he can sing anything -- opera, gospel, jazz. He's simply great.' "

Howard heard Martin sing and agreed wholeheartedly. "I was overwhelmed by his voice," Howard said, "and the fact that whatever kind of music he's singing, it goes straight to the heart and soul."

In addition to "Show Boat," Howard mentioned "Pippin" and the Leading Player but told Martin he'd have to audition for Kresley and Lala.

"We were concerned," Lala admitted. "He's an opera singer. But he sang for us from the 'Pippin' score in a contemporary pop vein and just blew us away. He also picks up movement very easily, which is good because he's got a lot of it to do. He's a very special talent with a flair and enthusiasm for musical theater that you don't often find in opera singers."

"James is a blast," said Pearce Wegener, who plays the title role of Pippin, Charlemagne's questing young son. "We do a lot of things together, so I don't feel so much like I'm alone onstage." At 21, Wegener says the role gives him the chance "to basically grow up in front of the audience. As Pippin, I'm playing every stage of what I'll eventually have to go through myself."

The original production period of "Pippin" on Broadway was one of the most contentious in musical theater history. Composer-lyricist Schwartz's idea of the show was very much like that of his previous hit, the gently jazzy "Godspell." Fosse's view of "Pippin" was that of sexy sorcery, as exemplified by the Leading Player's opening number, "Magic to Do." Fosse got his way by barring Schwartz from rehearsals, according to theater historian Ethan Mordden's "One More Kiss: Broadway in the 1970s." Mordden credits Fosse's "endless inventiveness" for the show's success, mixing sensuality, wholesomeness, cynicism and sentiment.

"You know what that's called?" Kresley said: "An audience show."