Whether the concert ends in a clattering brass fortissimo or a muted string diminuendo into silence, the maestro's performance is the same. After as long a pause as his back can sustain, 35-year-old conductor Michael Tilson Thomas wheels to face the audience. His shoulders are hunched, his face blank. He is unsmiling. He bows with a swooping grace worthy of Rudolf Nureyev.

Thomas says he is lost at such moments. "I have given everything to the piece," he explains, "and then there is this moment of confusion. Who is this person bowing to you? Only a few moments ago I was Beethoven, or Mozart, or Stravinsky."

He was Ravel three weeks ago in Milwaukee. Two weeks ago he was Rachmaninoff in Pittsburgh. With the Concertgebouw in Amsterdam this week he will be Charles Ives. Next week he is between jobs.

Of the 10 top symphony orchestras in the U.S., only the Cleveland has a native U.S. citizen as its full-time music director, and he will be gone soon. When Lorin Maazel takes over the Vienna State Opera the year after next, the usual lineup of Europeans will be the front-runners to replace him. Almost every top conductor would like to work with the orchestra, reports one agent whose firm does most of the major conductor placing, but then adds that not one of them will want to live in Cleveland. The Chicago's Sir Georg Solti says he has already declined the job, but the orchestra's management says it was not offered to him. And while other managers press their clients at the Cleveland's search committee, a lot of podium watchers will be raising the question—what about Michael Tilson Thomas?

He made his entrance at the top more than 10 years ago. He had been the assistant conductor for the august Boston Symphony Orchestra just two weeks when William Steinberg, its German-born music director, fell ill during a concert at Lincoln Center. "Steinberg came backstage after the Brahms," Thomas has said, "and told me, 'Put on your suit. I think you're going to conduct.' " Five minutes later the older conductor was on his way to the hospital, suffering from fatigue, and Thomas was onstage to make his New York debut. For the skinny 6'1" kid fresh out of the University of Southern California, it was uncannily like the launching of another understudy, Leonard Bernstein. Not long out of Harvard, he had taken the baton of the ailing Bruno Walter to lead the New York Philharmonic. That was in 1943, a year, month and week before Mike Thomas was born in Los Angeles. But as soon as he got to know him, Lennie pronounced Mike a genius too. "He's like me at that age," the grayed wunderkind said. "Except that he knows more than I did."

But he did not know about getting on as a new boy in the big-conductors' club. While Bernstein was on his way up, he rarely withheld any zesty revelations about himself and kissed everyone in sight, both verbally and literally. Maybe it was to outdo his role model that young Thomas took instead to cutting up his co-workers. "The thing that depresses me the most about my colleagues is their intense involvement with the rich," he told the New York Times in 1976. Then he lashed out at the musicians who were performing for him. He declared he was "tired of looking at people whose eyes were totally dead telling me, 'Oh no, this is not the nobility of Beethoven.' "

There was a lot of whining of that sort and tantrums at rehearsals whenever he turned up to conduct. When concertmasters and section leaders who had liked making the beginner look good began letting his inexperience show, the going got tough in important places for Maestro Mike. In Boston he had moved up as rapidly as a corporate board chairman's son-in-law: from assistant to associate to principal guest conductor in three years. But in 1973 when the top baton became available, he didn't get it (Seiji Ozawa did).

Thomas had settled earlier for a less glittering prize: music director of the second-rank Buffalo Philharmonic. Soon there were grumblings in that city too. Those putting up the money to get their orchestra back to work after a strike were not amused by the young maestro's conduct offstage. He had a rope swing rigged in his living room and padded around the downtown streets in his tennis whites. Neither his players nor his patrons ever knew for sure what music really struck the young man's fancy. He said he sang snatches of Monteverdi motets on peaks of Utah's Monument Valley, where he liked to walk alone. He played back-up piano for Sarah Vaughan, wrote songs with Art Garfunkel, savored the Rolling Stones and danced until dawn on visits to Manhattan's Studio 54. All of which kept that clergyman-sized moniker of his appearing in places where the Buffalo board of directors wished it would not.

Two years ago Thomas was arrested in New York after airport customs inspectors reportedly found a small amount of cocaine, three marijuana cigarettes and three and a half Dexedrine capsules in his luggage. The charge was plea-bargained down to disorderly conduct. It cost him a $150 fine and a temporary loss of his exuberance. "I was in a certain state of lamentation after that," he admits.

The incident has not had any effect on his career, Mike claims, but he admits that he is now out to remodel his reputation. "Some of the statements that I made years back about symphony orchestras being old fossils and about certain social scenes that were intolerable—those were in some ways accurate observations of what was going on. But they were also manifestations of my frustration at the time," he continues. "My God, I was so booked up then, giving eight million concerts all over the world, that there was no time left for me to remember what it was like to be young and crazy and on the scene. There was no place for any personal existence. I had to resolve that so I wouldn't resent what I do, which I don't. So what I'm trying to say," he sums up, "is that I am now a very serious and committed musician."

But he finds recognition of that recommitment growing faster in Europe than the U.S. He has been asked back for repeated, and longer, guest appearances. He has impressed the critics—and, as importantly, the musicians—by playing very unhackneyed programs and a lot of new music with the principal orchestras in Berlin, Paris and Rome. He also made a recording of Beethoven's Pastoral Symphony with the elegant English Chamber Orchestra in London. "If you told me 10 years ago that I was ever going to do that," he exclaims, "I'd have said, 'No way. It's such an old chestnut. So corny. With that ridiculous storm. A Walt Disney piece. I'd never do it.' So why have I done it? Because I've discovered tonal music."

With atonal music, his credentials have long been in good order. "From the earliest times in Los Angeles I can remember liking sour foods, abstract art and dissonant music." When he was 2, Thomas was dancing around the house to Stravinsky's Petrouchka, or so he has been told by his grandmother Bessie Thomashefsky, a celebrated siren of lower Manhattan's Yiddish theater in the early 1900s. Boris, her husband, was an Orson Welles prototype who acted in scores of shows he wrote, produced and directed, one being the first known version of Parsifal in Yiddish.

The conductor's mother is a Los Angeles public school teacher. His father, who shortened the family name, is a movie and TV producer who himself wrote scripts for his cousin Paul Muni. Mike was playing piano by ear when he was 5, and knew all nine Mahler symphonies at 15. Back then he was an oboe player in the North Hollywood High band. At USC, once he opted for music instead of crystallography and Asian studies, which were early enthusiasms, he became the conductor of the best youth orchestra in Los Angeles. As an undergraduate, he showed enough skill to be named Pierre Boulez's assistant both at new music concerts in Ojai, Calif. and at the tradition-bound performances of Parsifal at Germany's Bayreuth Festival (this time not in Yiddish).

Back on campus he accompanied violinist Jascha Heifetz, and cellist Gregor Piatigorsky picked Thomas as his pianist for master classes. In 1968 at Tanglewood in Lenox, Mass., where the Boston orchestra summers, Thomas won the Koussevitsky Prize for conducting the student orchestra, and that gave him the chance to help Erich Leinsdorf prepare the local production of Alban Berg's horror opera Wozzeck. The older conductor was astonished by the newcomer's familiarity with the enormously complex score. Thomas didn't tell him that between the halves of a USC football game a few years before, the marching band went through its formations while lining out music from Wozzeck adapted for al fresco performance by M.T. Thomas. Later he was conducting an assemblage of Boston-area amateurs when William Steinberg hired him to be his assistant. That city's symphony orchestra will never forget him—although he has not appeared with them in more than four years.

"I didn't fit into any of the easily defined categories," Thomas says now of the troubling talent he was then. "I am a new breed of character in this country." Dancing to Petrouchka and playing Wozzeck on football fields has, he thinks, given him a perspective on music that most of his elders cannot have. "What others call dissonances," he says, "seem to me beautifully muted and ambiguously woven tapestries with all sorts of wonderful browns and purples that I find very hard to separate. All you have to do is look around in the world now to see that dissonant, complicated, ambiguous music is a very true statement about the way things really are."

This century's most dissonant, complicated and ambiguous opera, Alban Berg's three-act Lulu, had its American premiere last summer in Santa Fe with Michael Tilson Thomas leading the orchestra. It was the very strong shocker it was meant to be onstage, but what rose from the pit, though rarely ambiguous, was an evenly woven tapestry of anguished sound.

It did more than touch off an explosion of great notices for the conductor, who said that preparing it was one of his happiest jobs. It led to some reputation-rehabilitating dates for him. Impresario Beverly Sills signed Thomas to conduct a new opera in the spring of 1981 for her New York City company.

With his eight-year stint in Buffalo at an end, Mike has shifted his base of operations to Manhattan and a fancy floor-through loft in the East Village which he shares with Josh Robison, his manager. Thomas can afford an expansive lifestyle. Though he has no podium to call his own—and may still lack the patron-placating, fund-dunning social skills that are a job prerequisite—his guest appearances give him an annual income in the $200,000 range. Last week he held a house-warming at a gala Passover seder. Mike, an excellent cook, who specializes in French, Italian and Chinese dishes, prepared the gefilte fish himself.

With his new, mature image, Thomas has put the drug and disco scenes behind him. "You won't see him in his manager's office in midtown in tennis clothes anymore," says an associate. "He's an adult now. I think of him as a maestro." But Mike Thomas does not regret his lost years. "I like a certain element of danger around me," he explained recently. "I like to walk to the farthest edge of the ice and then turn around and make it all the way back. That's what I think is really the essence for a performer."