John Aler began to dream about being a tenor while he was still a soprano.

That was in Baltimore where he grew up, where he was a boy soprano in St. Mary's (Catholic) Church and where he first began to dream about going out on a stage and belting out "Di quella pira" from "Il Trovatore" or "Esultate" from "Otello." He grew up in a music-loving family and caught the fever from old records (Mario del Monaco and Richard Tucker) and from television: "The Bell Telephone Hour," "The Voice of Firestone," even Ed Sullivan when he had an operatic guest star like Cesare Siepi.

Above all, he caught opera fever from the Metropolitan Opera's weekly broadcasts. "They were mandatory in our home," says Aler, now 41 and an internationally acclaimed tenor with a distinguished and growing list of recordings to his credit, who still goes back to St. Mary's most years to sing at the Christmas Eve midnight Mass.

John Aler never got to sing the kind of tenor roles he dreamed of doing -- such hair-on-chest, belt-it-out heroic tenor roles as Verdi's Otello, Manrico in "Il Trovatore," Radames in "Aida" or Alvaro in "La Forza del Destino." He is a tenore leggiero, a light tenor of the kind you hear in bel canto operas, in a lot of French repertoire, in Handel's "Messiah," which he sang with the National Symphony Orchestra this month, and most of all in Mozart's operas. He has sung Mozart all over Europe and the United States, and will be Tamino in the Washington Opera's "The Magic Flute," which will open tonight in the Eisenhower Theater.

This will be Aler's first performance in the Eisenhower, although he has sung before at the Kennedy Center, in the Terrace Theater and the Concert Hall, and he studied in Washington for five years at Catholic University.

Does he lament the prospect that he will never be a Manrico, Ernani or Alvaro? Aler's answer is thoughtful, circumspect and comically frank: "Oh, sure. ... That's what I was brought up on and what I dreamed about when I was a kid -- a lot of Verdi and Puccini, and I love it. I must say, though, I don't regret not singing it; what I really regret is that I won't make the big bucks that that repertoire pays, because if you can sing those, you can name your price just about anywhere. Certainly anybody would like a career like that, but I made my peace long ago with being a very lyric leggiero tenor, and there's a huge wealth of repertoire that I sing. And the reason I do this is because I love it and ... and ... for the money. I used to say I'm not in this business for the money, but I am. ...

"But what gives me the greatest pleasure is singing beautiful music with wonderful colleagues; there's nothing like it. There's no greater thrill."

He gets that kind of thrill all over the map. From here, he will go to London to sing in Mozart's "La Betulia Liberata" with the English Chamber Orchestra and Jeffrey Tate; then to Los Angeles to sing Benjamin Britten's "War Requiem" with Andre Previn; to New York for Bach cantatas with Erich Leinsdorf; to San Francisco for a duet recital with Benita Valente; to Switzerland and Spain for the role of Don Ottavio in "Don Giovanni." "I like to vary the menu a little bit," he says.

One way he keeps his menu varied is rooted in his hobby of browsing around old bookstores, specifically music bookstores. Get him started on the subject, and he becomes as lyrical as an opera by Donizetti:

"I have a pretty strong interest in -- what would you call it? -- arcane subjects, music that is slightly off the beaten track. ... I find some of the repertoire that interests me the most in dusty old back rooms. ... You feel mighty dirty after you come out of one of those shops -- you are mighty dirty -- but it's fun. ... I like to mooch around in the antiquaires ... old music shops in France. Almost every city has a little old music shop; there's a great one in Toulouse, a good one in Lyon, a couple of wonderful ones in Paris, and I love to collect old scores and old sheet music... .

"One of my great finds was a few years ago; Duparc wrote only about 12 songs, but he wrote a duet for soprano and tenor, and I happened to find it in Brussels ... in Vienna, at Doblinger's, in the back. Years ago, there, I found a score of 'The Rape of Lucretia' with an autograph of Benjamin Britten and one of Peter Pears from 1949... . That cost me about $11 ... and with the autographs it's priceless.

"I've found lots of songs that I'd love to perform and record. Some great songs by Reynaldo Hahn ... beautiful songs. There's a composer called Dupont -- Gabriel Dupont -- that Danny {pianist Daniel Blumenthal} found. He wrote some wonderful songs that we're going to try to record next year. He wrote several operas that really look good, but it's very difficult to get a recording of an opera put together, very expensive."

His taste for the odd corners of the light tenor repertoire harmonizes well with the kind of voice he was born with and the kind of training he has given it. It also harmonizes with the taste of a growing proportion of the classical music audience. "It's a good time to have that kind of voice," he believes, "because that repertoire is really being investigated now, and not just the surface things, the things that are well known to everyone, but also some of the really obscure things that are lots of fun to sing and deserve a hearing."

Tamino, like Ottavio in "Don Giovanni," is part of Aler's less obscure repertoire and a prime source of income. Both roles have extraordinarily good music but characters far different from the sword-waving Verdi heroes of Aler's youthful fantasies. Ottavio is supposed to punish Don Giovanni for his attempted rape of Donna Anna, and he talks about it a lot, but the punishment is finally dealt out by a statue that comes to life and drags the villain down to Hell.

Tamino, the first person seen in "The Magic Flute," rushes onstage pursued by a dragon and promptly faints. How does Aler feel about portraying such wimps? He feels fine, after becoming deeply acquainted with the characters through many performances.

"Ottavio is really the only person in the opera {"Don Giovanni"} who maintains his sense of dignity, his sense of himself," Aler says. "All the others are so obnoxious, with such super egos. But Ottavio is the only one who is there in support of someone else ... altruistic ... trying desperately to maintain his integrity in an untenable situation. Tamino can seem like a kind of a wooden character ... silly, superficial, passive. But he {goes through} a rite of passage, finding himself and his manhood, a sense of responsibility and altruism. I think of the stages of childhood, when children find an altruistic side of their character and actually do things and take responsibility for others. ... if this step isn't taken in early childhood, it makes great difficulty later. I think Tamino is an allegory for all of us about taking responsibility. ... There is always something external to conquer, but the real conquest is an internal process."

He is glad that he does not have to produce any music on the flute that he will carry through his adventures in the Kennedy Center -- someone in the orchestra pit will take care of that. "Have you ever tried to play a flute?" he asks. "It's the hardest thing; even to make a noise on it, even the most ghastly noise, is for me next to impossible. ... Luckily, this is a magic flute, so if the person doesn't look like he's playing exactly right, it can work anyway. I've even done productions of the opera where you just hold the flute up and, sure enough, it plays itself."