"My father wanted me to be a doctor," says John Mauceri. "The thought of his son becoming a musician horrified him--perhaps because his father was a musician in the Depression."

For John Mauceri, growing up in Queens and Long Island in the 1950s, the influence of his grandfather, Baldassare Mauceri, prevailed over the economic worries of his father, who is a doctor.

Tonight, John Mauceri raises his baton to conduct the National Symphony Orchestra at the Kennedy Center in "Das Rheingold"--the first Washington performance of Wagner's epic composition in more than half a century. Next week, Mauceri flies to London, where he will conduct 15 performances of "Madame Butterfly" and "La Bohe me" at Covent Garden. But he will be in Washington from time to time throughout the season to audition new players for the Opera House Orchestra (which he serves as music director), to conduct the Washington Opera's production of Offenbach's "La Belle He'le ne" and to conduct the Washington premiere of Leonard Bernstein's new opera, "A Quiet Place."

At 37, when he is not busy in London or Washington, Mauceri has a full calendar of conducting assignments that span the map from San Francisco to Vienna, and occasionally he drops in to conduct his Broadway production of "On Your Toes," which he launched with Roger Stevens at the Kennedy Center last year and which won two "Tonys" this year. In his almost nonexistent spare time, he is an adjunct professor of music at Yale, where he began as a premed student in 1963.

Mauceri's involvement with music and theater began in Queens when he was 5 years old, and started taking piano lessons and staging his own juvenile productions of shows he had seen on television, using playmates when he could get them to cooperate and homemade puppets when he couldn't. His childhood enthusiasm still creeps into his voice when he talks about musical theater, whether it is a long-forgotten Broadway show or Wagner's massive "Ring" cycle, which he considers "one of the 10 greatest works of art produced by western man."

"One reason why I'm so interested in musical theater," he says, "is that it's one of the strongest media for passing information from one generation to another. When we decided to do 'On Your Toes' in the style of the 1930s--a style as lost today as the original way of performing Handel--we brought in George Abbott, the original director, who is 96 years old, as well as Balanchine, who was in his eighties and Hans Spialek, who did the original orchestration and was in his nineties. One of my great experiences in that production was watching my 6-year-old son, Ben, seriously talking with Abbott about small technical details of the production. Here we had a man who came out of the 19th century sharing his experience with a boy whose life should go on well into the 21st."

At an earlier point in his life, when his primary job was teaching at Yale and conducting the Yale Symphony, Mauceri's academic work meant financial security as well as job satisfaction. Then, his conducting engagements began to increase, partly with the assistance of people he met during the summer at places like Tanglewood and Bayreuth.

On a visit to Bayreuth, he ran into a young American named Mike Thomas, who later developed into conductor and pianist Michael Tilson Thomas and helped Mauceri to build his career. Even more significant was his meeting with Leonard Bernstein when Mauceri was a conducting fellow at Tanglewood in 1971. "Bernstein totally changed my life," he says. "From him, I learned the imperative of total commitment to music." He worked as an assistant to Bernstein for the 1972 production of "Mass" at the Kennedy Center and then for "Carmen" at the Metropolitan Opera. At Yale, he produced his own interpretation of "Mass," which differed significantly from Bernstein's--making the Celebrant an older man, for example. This was the production used for the work's European premiere in Vienna. Later, he produced an adaptation of Bernstein's "Candide" that is the basis for the long-running production at the Arena Stage.

Composer Gian Carlo Menotti attended Mauceri's Wolf Trap production of "The Saint of Bleecker Street"--his professional debut 10 years ago this month--and liked it so much that he invited him to conduct at the Spoleto Festival. Today, Mauceri no longer has as much time for teaching as he would like; his position at Yale, he says, "allows me to drop in and teach from time to time as my other commitments permit."

As his conducting assignments grew, Mauceri recalls, "My wife Betty and I decided we would try taking a year off from Yale to live on conducting. When we began, we had $10,000 in the bank and at the end of the year we had $9,000, so it cost only $1,000 to do a year of conducting. Now, it costs me more than they pay me to go to Yale and teach, but I plan to continue. I owe a lot to Yale, and I think I have a responsibility to maintain contact with young people and share with them what I have learned. Besides, I enjoy it."

In a nonmusical household, John Mauceri learned music the hard way--by himself. At public school in Queens, he says, "we had a music appreciation class where we would sit and listen to scratchy old 78s--except that I was the only one who listened. When I was seven, I could remember any piece of music and pick it out on the piano. People had trouble convincing me that I should bother learning to read music."

Then as now, he divided his interest about evenly between Broadway and the opera house. When he was 8 or 9, he saw a televised performance of "Madame Butterfly," then "literally saved up my pennies until I could buy the record." A few years later, when he was about 11, it was the movie of "The King and I." "I went home and wrote out a script for it and recruited friends for a back-yard production," he says. He discovered Wagner when he was 15 and was familiar with a few Italian operas: "I heard 'Tristan' on the radio and was fascinated with its form--the way the music of the Prelude comes back at the conclusion of Act I. I got the records and listened to them every night while I was doing my homework, but I stayed on Act I for a long time. There was so much there that it was months before I dared to go on."

Also in his 15th year, 1960, a New York radio station devoted an entire day of programming to a broadcast of the complete "Ring" cycle from Bayreuth--the first time Birgit Nilsson sang a complete "Ring." Mauceri spent the entire day taping it. "At that time, there was no complete 'Ring' available on records," he says, "and I lived on those tapes; I still have them. My brother and I went through the score and marked all the leitmotifs and made a catalogue of them. Now, when I'm rehearsing 'Das Rheingold,' I look down at the score I'm using and it's the same one; I see notes there in my brother's handwriting."

That summer, when his parents went on vacation, they left him at home with instructions to paint the house. "For two weeks, while they were away," he says, "I spent every day painting with my Wollensack tape recorder on the floor playing the 'Ring.' With the money my parents gave me for painting the house, I went out and bought 'Parsifal' and Verdi's Requiem."

At Yale, after deciding that he would not become a doctor, Mauceri plunged into music studies in all directions, taking courses in piano, voice and composition. But it was not until he took a conducting class with Gustav Meier that he found his place in music. "That night," he says, "I went back and told my roommates, 'For the first time, I feel that what I am doing is right.'" By his senior year, he was producing an opera (Britten's "Curlew River") at Yale.

Conducting seems a natural choice of vocation for someone who was organizing a performance of "The King and I" in his back yard before he reached his teens. "I have always been an organizer and a leader," he says matter-of-factly, "and I have very definite feelings about how things should go."

Washington, which has become almost his second home since his debut 10 years ago, is one city where these feelings are respected, whether he wants to produce "On Your Toes" in its original style or "Das Rheingold" exactly the way Wagner wrote it. "One thing I like about Washington is the positive attitude I find here," Mauceri says. "I am always taken seriously, even when I want something that must seem outrageous. When we started talking about doing 'Rheingold,' NSO executive director Henry Fogel asked me, 'How many anvils will you need,' and I said, '18.' You can do it with three; I hear the Chicago Symphony does it with three. Even at Bayreuth, there is some question whether they always use 18 tuned anvils--but you can't tell because the orchestra is kept out of sight."

Tonight, Mauceri will be conducting 18 tuned anvils.