Jon Kalbfleisch was a 19-year-old pianist in Lawton, Okla., when the local community theater asked him to be music director for their production of "Gypsy." He would have a half-dozen musicians to work with.

"I said, 'No! 22!' " Kalbfleisch recalls. "I went out and begged 22 people to play. And they did."

Taking care of the music in musical theater turned into an unexpected career for the classically trained Kalbfleisch. He has set an exacting standard at Signature Theatre since the company's first musical in 1991, which was no less a venture than Stephen Sondheim's "Sweeney Todd."

"We could have performed this with three synthesizers," Signature Artistic Director Eric Schaeffer told The Washington Post at the time, "but our musical director felt if we're going to do it, we're going to do it right." An orchestra of 15 made a big impression in a small Arlington space, and Schaeffer thinks it was a decade before the troupe used a music director other than Jon K., as Kalbfleisch is known.

"He really respects what the writer has put on the page," says Schaeffer, who is now directing Sondheim's "A Little Night Music" — the 1973 waltz-infused romance that features "Send in the Clowns" — with his longtime music director.

Neck-and-neck with "Sweeney," "A Little Night Music" is Kalbfleisch's favorite score ("The grace, the warmth," he says). The affection shows as he describes the comic chaos of "A Weekend in the Country," the giddy Act 1 finish with rivals in a lather.

"I particularly enjoy making sure it sounds like everybody's singing the same thing, that the phrasing matches, the vowels match and the diction's clear," Kalbfleisch says. "Getting the ensemble singing as clear and clean and accurately as possible."

Washington audiences might take for granted Signature's stylistic navigation of rave-outs such as "Hedwig and the Angry Inch," or the symphonic luster of Leonard Bernstein's "West Side Story," Andrew Lloyd Webber's "Sunset Boulevard" and practically the entire Sondheim canon. Less noted is the high musical standard set for a region that lately has dramatically upped its game.

Last year, Round House Theatre produced its biggest musical ever, the daunting "Caroline, or Change." Artistic Director Ryan Rilette, who came to Round House five years ago after running the San Francisco area's Marin Theatre Company, hired Kalbfleisch and heeded his guidance to use the full orchestration for composer Jeanine Tesori's fusion of Jewish and African American traditions. "In the Bay Area," Rilette says, "there's nothing similar to Signature, and no one similar to Jon."

Musicals are new to Baltimore's Everyman Theatre, too. So associate artistic director Noah Himmelstein, who directed last year's extravagant Andrew Lippa oratorios "I Am Harvey Milk" and "I Am Anne Hutchinson" with Kristin Chenoweth at Strathmore, recruited Kalbfleisch for composer Michael John LaChiusa's two character, musically fluid "Los Otros" in the spring.

"He brought so much knowledge of Michael John's work," Himmelstein says of the 90-minute chamber piece, which spans decades and hops the U.S.-Mexican border. "It's so detailed. Everything is in the score — all the thoughts and subtext."

The funny thing is that Kalbfleisch is no Broadway baby, with a pulse throbbing to show tunes. How he fell for music at all is a mystery, because it wasn't dominant growing up in his Lawton household. But he quickly took to piano once lessons started at age 8, and by high school, a teacher pressed him about playing for the student musical.

"This could be better," Kalbfleisch thought as he watched what was going on. "I don't know how I knew that."

He studied piano at Lawton's Cameron University and then went to Southern Methodist University in Dallas for graduate work in conducting. That's what he wanted — a classical career, with symphonies, opera and ballet. And he's having that: In addition to conducting "Les Miserables" on tour and on Broadway and serving as music director and organist at Capitol Hill United Methodist Church (where he programs a concert series), he has been music director and conductor of the Lawton Philharmonic for a decade. Violinist David Kim, concertmaster for the Philadelphia Orchestra since 1999, has played Oklahoma several times for Kalbfleisch.

"Lawton really benefits from having a hometown boy who is this fantastic conductor," says Kim, who will perform Bruch's Violin Concerto in Lawton this month.

After college, however, the ready gigs were in musicals. When Kalbfleisch got a call to do "A Chorus Line," the director wanted to give him five musicians. Kalbfleisch noted that nearby university students would probably love to tackle Marvin Hamlisch's swaggering film noir score for practically no money. "Sure enough, everybody wanted to play it," Kalbfleisch recalls. "We did it with the complete orchestration, and blew everybody out of the room."

That was frequently the response as Signature — to which Kalbfleisch latched on almost immediately after moving to Washington — built its reputation in "the garage," the cozy converted space it occupied for more than a decade. After the startlingly effective "Sweeney," Signature staged the area premieres of Sondheim's newer "Assassins" in 1992 and "Passion" in 1996.

"That was the first one Sondheim came to," Kalbfleisch recalls of "Passion." "He stayed through the play-out music, then he stood and . . . " Kalbfleisch claps. "I thought: 'Wow. That was nice.' Then we all went to dinner and chatted." (Chilling with Chita Rivera as she starred in and he conducted John Kander and Fred Ebb's "The Visit" at Signature in 2008 is another "how-did-I-get-here?" moment.)

A smart revival of "Cabaret" led Kander and Ebb to premiere their new (though ill-fated) "Over and Over" at Signature in 1999. " 'Cabaret' may have been the first one when we put the band up and behind the stage," Kalbfleisch says. "It sounded great. And then, to the technical director's dismay, we built platforms for every show and put the band up there. There were amazing moments in there. And it wasn't miked. The sound was really immediate."

Signature's rapid acclaim meant opportunity (talented people wanted to work there) and challenges (paying union wages, living within budgets, staging big shows in tight quarters). Positioning the musicians was so key that when Signature moved into its new, two-stage headquarters in 2007, the main theater was equipped with a balcony around the entire perimeter, in part so the orchestra can be situated anywhere. The gung-ho garage ethos of reconfiguring the stage and audience show by show is still a Signature hallmark. And even if the company gradually gave in to amplification, care has been taken not to let it erode musicality.

"Sound reinforcement has gotten progressively better," Kalbfleisch says. "You still feel like you're hearing people sing from the stage, instead of only through a speaker."

"Professorial" and "patient" are words that frequently come up describing Kalbfleisch, which makes it funny when he breaks expectations. Rehearsing "A Little Night Music," singers were astonished when a rhythm caught his attention and he worked it through to its source: Beyonce's "All the Single Ladies."

"Jon K!" they gushed.

"I listen to everything," he says.

He also hears everything. Signature co-founder Donna Migliaccio, currently understudying Patti LuPone in Broadway's "War Paint," says, "He really is amazing in being able to single out who's going wrong."

When that happens, there is a Jon K. "look," an over-the-eyeglasses stare. "He knows he does it," Schaeffer says.

Migliaccio got the look when she first played Mrs. Lovett in "Sweeney" and bailed out on a climax. "I don't think Mrs. Lovett would sing that note," she absurdly reasoned. When she played Lovett again in a later production, Kalbfleisch insisted on sticking with the score. "Eventually," Migliaccio says, "he gets his way."