Though he sang with ethereal plangency, however, Deller couldn't act. When James Bowman took over the tailor-made role which Deller could not handle - Oberon in Britten's Midsummer Night's Dream - a new game began. Bowman's voice had a clarion quality, and his stage presence was quintessentially masculine: with a role-model like this, it was inevitable that the countertenor would become fashionable.
But the next wave of countertenors were not all Bowman-clones. The Belgian Rene Jacobs infused the voice with melting femininity; the East German Jochen Kowalski injected more than a touch of camp; the black American Derek Lee Ragin came across like a diva. Moreover, national schools began to emerge. As Bowman once explained to me: "Americans like a brash, wobbly sound and despise the clean English style. The Germans tend to be over- dramatic, though not as hysterical as the Americans. The French style is insufferably affected, a stabbing at the notes."
The countertenor voice is produced by using the edge of the vocal cords and neglecting the central part, which in men is the bass area: it's like playing harmonics on a violin. Unnatural? Not necessarily. For Artur Stefanowicz, currently starring with great panache in Martha Clarke's Orpheus and Euridice at ENO, there was never any other option. When he joined a boys' choir in his native Szczecin it was as an eight-year-old alto, and when his voice broke he simply went on singing the same notes falsetto. He reluctantly went on to train as a baritone - professional countertenors were unheard-of at that time in Poland - and it was only when he chanced to hear an amateur that he realised his vocation. "I always found it stressful singing baritone, whereas falsetto felt easy and natural." So natural that at 23 he won the European Mozart Competition.
One of Stefanowicz's formative experiences was hearing Michael Chance sing in Bach's Mass in B minor. "It was like an angel, unbelievable - I'd never heard anything so beautiful in my life. I decided I wanted to sing like him."
Over now to Chance himself, whose voice does indeed have an angelic purity, and who happens to have a record just out (The Art of the Countertenor, on Deutsche Grammaphon). Chance's exemplars include Peter Pears and Janet Baker (as well as Deller and Bowman), but he gravitated as naturally as Stefanowicz did to singing falsetto. His record may be largely Baroque, but he is opposed to the root-and-branch recolonisation of that disputed terrain. "The countertenor should not be the only voice we hear in the alto parts in Messiah or the St Matthew Passion. Mezzos shouldn't be banished completely."
Moreover, Chance has systematically expanded the contemporary repertoire by singing specially commissioned works from the likes of Tan Dun, Judith Weir and Harrison Birtwistle. Accompanied by five viols, he is soon to premiere the mystically-titled Nipson (Cleansing), a half-hour work by John Tavener, and he's even premiered a piece by Elvis Costello ("but I wouldn't urge you to listen to it"). The countertenor voice, he agrees, has a big future and, as he points out, it's been staple fare in rock from The Beach Boys onwards. One thinks also of the satanic Martyn Jacques, currently wowing London audiences in Shockheaded Peter at the Lyric, Hammersmith, and on the CD from Warners.
All of which brings us to the extraordinary Andreas Scholl. Taught by Jacobs and examined by Bowman, this Clark Kent look-alike from Wiesbaden has taken the opera world by storm, following a heartstopping performance in Rodelinda (alongside Stefanowicz) with a flood of recordings, including three in this month alone from Harmonia Mundi, DG, and Decca.
But what Scholl really wants to talk about is his parallel life as a pop musician. He made a pop record a few years ago which flopped, but his second shot - a collaborative effort conceived, composed, and part- performed by him in his own hi-tech studio - sounds promising. "Soul- funk for a grown-up audience" is his shorthand description, and he stresses that it will have no whiff of "crossover". "I shall do it with the same conviction that I bring to Baroque music," he insists, adding scornfully that he in no way shares contemporary composers' "fear of beauty". Stand by for something interesting on Decca next Christmas.
Meanwhile, he has applied for his old tutor's job at Basel, where fledgling countertenors are starting to proliferate. How have things changed since his own student days? "Enormously. Countertenors can no longer trade on their exoticism. Originally it was enough to sing high, whether in tune or not, beautifully or not. Now they have to be good."