If history explains why so many counter-tenors are British - the modern tradition dates back to 1943, when the conductor Walter Goehr and composer Michael Tippett first "discovered" the male alto Alfred Deller singing in Canterbury Cathedral and, in Tippett's words, "the centuries rolled back" - it is harder to understand why the style should have attracted a young Japanese-American, living on the West Coast, whose earliest memory of falsetto singing is in the music of Seventies funksters Earth, Wind and Fire. Yet Brian Asawa, who sings the castrato role of Tolomeo (Ptolemy) in the Royal Opera's Giulio Cesare, is fast gaining a reputation as one of the most exciting voices in baroque and beyond.
Despite his Asian origins, Asawa's early experience pointed him towards Western classical music: "My only contact with Japanese music was with old folksongs that my mother sang." His parents enrolled him in the Yamaha School of Music, where he began piano lessons at the age of five. "In junior high school, I took up the cello, and sang in the church choir. Then I took up trombone so that I could play in marching band competitions, a big Amerian high school tradition. I sang, but I didn't take one-on- one voice lessons."
In fact, when he entered the University of California, Santa Cruz, it was as a piano major; he only switched to voice at the end of his first year, singing tenor in the choir. "The campus was in a redwood forest; it was like being in summer camp all year long. I would walk through the forest back to the dorms after rehearsals, and amused myself by singing the soprano line in the music we'd just been rehearsing. It was something I really enjoyed and I discovered I had a strong falsetto."
One wonders what Asawa's fellow students made of the male soprano voice echoing through the redwoods. Luckily, his voice teacher was familiar with baroque repertoire, and encouraged him to switch voice type. Asawa graduated in 1989, and in 1991 became the first counter-tenor to win the Metropolitan Opera auditions, making his mark with a voice that is unusually rich and well-supported, certainly in comparison to the sound of European counter-tenors.
In that, he may simply be reflecting a cultural difference: "America counter-tenors strive for a richer sound, perhaps because we're not brought up in the English church tradition of boy sopranos. But early music in general is evolving towards a singing style that's fuller, as opposed to the thinner, whiter sound preferred when the tradition was started. There are different styles in every country: in Germany, for example, you have Jochen Kowalski and Axel Kohler, who have a more operatic style; and you have Andreas Scholl, who has a generally lighter approach with sparing vibrato."
For Asawa, vibrato is an essential tool: "Every voice vibrates, so that when you're singing straight tone [without vibrato], you're restricting something in the voice. Singing straight tone too much can be detrimental to healthy vocal production." Not that he eschews it altogether. "It's a question of context: when, in an opera, a character is sighing, in love or whatever, oftentimes a lighter, straighter sound is appropriate. When the character is angry, one lets loose."
Although Asawa has focused on the baroque, he has occasionally ventured beyond the counter-tenor's normal domain. In concert, he has, for example, sung Cherubino, the hormonally excited page in Mozart's Marriage of Figaro, and a role usually sung by womanly mezzos. "Some might see that as a betrayal," he admits, "because the role was written for a woman, and Viennese audiences loved that erotic element of a woman playing a horny boy. But I think it would be an interesting thing to try on stage: as a man, I know what it was like when I was 15; and why not look the part?"
Quite what credentials he had to play Baba, the bearded lady in Stravinsky's Hogarthian opera The Rake's Progress, is anyone's guess, but the cross- dressing is clearly becoming a habit: there has even been talk of his taking on the soprano part (a child's view of heaven) in Mahler's Fourth Symphony. His latest CD, The Dark Is My Delight (on RCA Victor), may be of lute songs by Dowland and Campion, but his next will be of late- Romantic songs by Faure, Medtner, Rachmaninov and Villa-Lobos. He's also sung Schubert in recital. "Any of the song repertoire seems fair game," he says. "It's a matter of making intelligent, careful selection of material that's best for me. I love the Romantic period. I'll see a Mascagni opera, and think, `Damn! I wish he'd written something for me'."
Yet, while there is a growing corpus of contemporary songs for counter- tenor, in opera there has been no more than a trickle of new counter-tenor roles since Britten wrote the part of Oberon for Alfred Deller in his 1960 Midsummer Night's Dream. As Asawa laments, "Contemporary music tends to identify the counter-tenor voice as something other-wordly, or as representing simply youth. Maybe composers are just not ready for a counter-tenor voice to depict a normal, grown male."
Which is where Handel comes in. Tolomeo, in Giulio Cesare, is absolutely a normal, grown male - ambitious, vindictive, jealous and lustful - and, in the absence of castrati, Asawa's voice - rich, warm and most definitely adult - is just the one to sing it.
`Giulio Cesare': from tomorrow, Shaftesbury Theatre, WC2 (0171-304 4000)