Take a good look at James Conlon when he conducts the National Symphony Orchestra tonight on the Capitol lawn. It will be a rare chance to see one of this country's most distinctive musical talents in action.

For all practical purposes, America has lost Conlon to Europe -- partly because he has had offers he couldn't refuse and partly because he likes living close to his cultural roots. But he says he also likes "the quality of listening" he gets from audiences there -- even more in Eastern than in Western Europe.

"The New Grove Dictionary of American Music" sums up some of his qualities: "Conlon has carefully considered each step in his musical and professional development. His highly serious approach to music is offset by an almost childlike delight in performing it."

The 37-year-old New Yorker is no longer a boy wonder as he was in 1971 when his conducting first caught the world's attention. But he is one of the few international star musicians who can look you in the eye and say "Music to me is a great spiritual force" and make you believe he means it. Music director of the Rotterdam Philharmonic since 1983, he has just renewed his contract through the 1990-91 season. He has also accepted an appointment as chief conductor of the Cologne Opera, beginning with the 1989-90 season. And that means that his native land won't be seeing much of him from now on.

"Two jobs like that don't give you much time for guest conducting," he says. "I'll be in that part of the world 90 percent of the year. What does that leave for America? It means" -- he pauses -- "two weeks a year; three weeks a year maximum."

In America, it is getting easy to hear Conlon on records while it is getting hard to see him in person. He is one of the busiest classical performers on the Erato label, currently reaping critical superlatives for recordings of Mozart with the Scottish Chamber Orchestra and Liszt with the Rotterdam Philharmonic. One of his most remarkable recent recordings is "Christus," a totally unfamiliar, gently lyric Liszt oratorio with a Latin text, and he hopes to record a companion oratorio, "The Legend of Saint Elizabeth," which he calls "another great work that is not known."

Closer to box-office realism, he has also begun conducting the sound tracks for opera movies, fulfilling a long-held ambition. For an Erato film, Conlon has taped a "La Bohe`me" sound track -- his first operatic recording.

"I believe deeply in operatic movies," he says. "This was a dream of mine even when I was a teen-ager. The only one doing them at that time was Karajan, but they are coming of age now, and I am convinced that they are going to be the largest boon to opera since recordings ... They break down all of the barriers that have kept our American audiences away. You don't have to go to a city that has an opera house. You don't have to be put off by tuxedos ... You don't have to be put off by language now with the subtitles ... "

Through all the transatlantic years of his career, first as a "have baton, will travel" free-lance conductor and more recently as the music director in Rotterdam, Conlon has always kept his Manhattan apartment near Lincoln Center. Even if he didn't spend much time there, it kept him attached to the city where he began to dream about conducting when he was only 13, where he studied violin, piano and voice at the High School of Music and Art, and where he conducted a "La Bohe`me" at the Juilliard School, while still a 21-year-old undergraduate, that attracted international attention and guest-conducting assignments.

He has recently moved out of the old New York apartment but only because, as a newlywed, he needed to move into a bigger one. When will he use it? Probably mostly on vacations and when he is conducting at the Metropolitan Opera, where he began conducting when he was 26. "I love the Met," he says. "I love working there, but I can't be there all the time. I conducted 'Khovanshchina' there this year, I did 'Boris' there last year; now I won't be back until 1991."

Otherwise, his American agenda includes three Verdi productions for the Chicago Lyric Opera over three seasons, a few concerts with the Chicago Symphony and little more. He may pop into his apartment next year when he zooms across the U.S. on a tour with the Rotterdam Philharmonic that will not include Washington.

Strictly speaking, Conlon's connection to Europe dates all the way back to his professional debut, at the Spoleto Festival in Italy when he was 21. The opera was "Boris Godunov" -- his favorite; he began his career by fulfilling a lifelong ambition. "Boris," he says, was "a childhood love; it goes back to the time I was 13 years old. I can't explain it in any other way than to say that I fell in love with 'Boris' on first hearing. It made a deep impression on me and it led to my wanting to read Dostoevski when I was 14 years old. It was overwhelming; it opened up a world to me."

Conlon thinks he was lucky to get his start so young but even luckier not to succumb to the pitfalls of early success. "There are tremendous disadvantages to being successful young," he says. "It's fortunate because it removes a whole period of insecurity about 'will I be able to make a living,' and that's good. On the other hand, it can be fraught with danger if you're not careful. My opinion from the beginning was that I wanted to survive and I wanted to conduct all my life. I can't tell anyone else how to plan a career; I just don't know." But he does know that getting invitations to conduct in Europe is only the first step in building a career; some assignments are suitable and some aren't, and a young conductor has to learn "what's important to you and what isn't." Also how and when to say no: "In the course of time, you weed them out and they weed you out."

For him, the attraction of Europe has grown steadily stronger, Conlon says: "I started going to Europe sort of as if you were going on your junior year abroad, to get cultured up, only to discover that you can't get cultured up in three months, then to go back to more and more until I ended up wanting to live there. That's a big change. I would not have expected, 10 years ago, that I could live happily away from America ... Now, I don't see that I could live without Europe."

This sentiment brings to mind the closing paragraph of a book by William Murray, which Conlon quotes from memory, like something that is a part of himself: " 'I stand between two continents like a colossus with one foot on each continent. The result is, when I am in Europe I yearn for America, and when I am in America I yearn for Europe.' "

"The richness and breadth of cultural reference in Europe is irreplaceable," he says, "the impressions and sensations you have living closer to the source where most of this music has come from. It's an illusion to think that Paris of 1987 is the Paris of Debussy or Bizet; it's an illusion to think that you know Mozart because you had coffee in Salzburg or because you spent a summer course in the Mozarteum. But proximity to the language is very important; proximity to the visual arts, to the architecture, to churches, to the weather, to all of it ... You can't run into a museum and come out and say, 'Now I've seen this work of art, I can conduct this piece.' It's not like that. It's a slow kind of osmosis that takes place over a long period of time by hearing a language spoken around you. That somehow gradually becomes integrated with the music."