It's simple: American Ballet Theatre is one of the premier classical dance companies in the world. Founded in 1937 by former Bolhoi dancer Mikhail Mord, its artistic directors have included, from 1980 to 1989, Mikhail Baryshnikov.

It held its Opening Night Fall Gala Oct. 31 - Sigourney Weaver was among the starry attendees - and the company began its autumn run of shows Nov. 1 at the David H. Koch Theater at Lincoln Center.

Conducting today's performance? ABT's conductor and music administrator David LaMarche, a Westerly native who graduated in 1973 from Saint Bernard High School in Uncasville.

LaMarche is one of three ABT conductors. They divide up performances with the orchestra that usually runs between 55 and 60 musicians - one of whom happens to be fellow Saint Bernard Class of '73 grad Richard Clymer, who plays trumpet.

LaMarche began working with ABT in 1999 on a part-time basis, after he was a rehearsal pianist and then conductor for the Dance Theatre of Harlem. He went full time in 2000.

Discussing conducting for a ballet company, LaMarche says, "The thing is, dancers and musicians have different needs. For dancers, it's a form of expression. They want to feel comfortable also, because they're doing something very difficult. It takes lot of concentration and physical strength.

"At the same time, the piece of music that accompanies the dance has its own world - it has to sound good, it can't be too slow. We have discussions all the time, and a lot of the time, we compromise. ... My job is to find a way to make the music sound organic and good and still satisfy the needs of the dancers."

Usually, LaMarche will go into the studio where the dancers are rehearsing. He'll conduct the piano accompanist to find what the best tempo and interpretation might be. If there's a discussion to be had or a disagreement to be ironed out, this is where it happens.

An example of the kind of thing a conductor might consider: "If a step is very difficult technically, then sometimes dancers would need a little more space in the music - maybe a slightly slower tempo. A lot of times, it's not even tempo, it's just how it's played," LaMarche says.

For classical ballets like "Swan Lake" or "Giselle," he says, the ballerina has a lot of solos, and each dancer does those solos completely differently. In those cases, a conductor has to keep a close eye on the performer during the shows and adjust as needed.

LaMarche began in music as a pianist. His father asked the young LaMarche if he wanted to study an instrument. LaMarche was interested in the clarinet, but since his grandmother had a piano, his father suggested he try that.

When he was a student at Saint Bernard, LaMarche played in the orchestra for school musicals like "West Side Story" and "Bye Bye Birdie." He says they were lucky to have a great music director, Robert Brouillard, and productions that were actually more than school musicals - they were combined efforts of students and professionals from the theater community.

"I always enjoyed the collaborative thing when you're in some sort of theatrical presentation with music and other things, like acting or dancing," he adds, adding that his work with ballet companies is, in a way, an offshoot of that.

LaMarche was majoring in foreign languages - French and German - at Boston University when he decided to switch his focus to music. (He also took some dance lessons while at BU.)

After graduating in 1977 with a music concentration with a liberal arts background, he moved to San Francisco. During his five years there, he started accompanying dance classes as a pianist.

"I was living in Haight-Ashbury in a hippie commune type house with 12 people. One of my roommates was a dancer. I was looking for work, and he said, 'Have you ever accompanied a dance class?' I said no. He said, 'Come to look at one and see if you like it.'"

So he stopped to watch the class - and found his niche.

"I just knew instantly that I had this facility, this aptitude for translating movement into music and started making them sync together," he says.

When he moved to New York, he looked for the same sort of work because he enjoyed it.

LaMarche hadn't considered conducting, but Arthur Mitchell, co-founder of the Dance Theatre of Harlem, saw potential. He asked if LaMarche wanted to try conducting. He did. It went well, and he enjoyed it.

"It's trying to communicate something nonverbally. A conductor is like an electrical conductor, you know- you facilitate a flow of energy between people," he says.

He sees himself as a link between the audience and the stage.

"In any kind of performance, there has to be a flow of energy between all the participants. The audience is a participant in the performance. Sometimes we think audiences are passive, but they're not. They participate by their responses, by how focused they are. I always feel the music is one way the audience can latch onto the performance and connect to what's going on onstage," he says.

ABT performs in New York City, of course, but also regularly travels to places like Washington, D.C., and Los Angeles. Usually, once a year, there's a tour to Asia, where there's a huge fan base for ballet.

LaMarche keeps up with his piano playing, doing solos for the ballet company from time to time.

He also played piano at last year's Kennedy Center Honors for the segment celebrating ballerina Natalia Makarova. Among the other honorees in the wildly eclectic mix: Dustin Hoffman and the members of Led Zeppelin.

"You're all herded together in this waiting room backstage, before the performance, and there's all these different types - there's ballet dancers and heavy metal musicians ... It's really funny, actually," LaMarche says.