The golden boy: Countertenor Iestyn Davies talks high notes, low moments and hissy fits

What is a countertenor? One answer is the Beach Boys, and everyone who has come after them, singing high in pop. You could go further back and include barbershop singing, or look abroad to Malta, where high-voiced male ghana folk music goes back centuries. But the word "countertenor" was invented in medieval England, and in the Renaissance it denoted several things: a tenor singing at the top of his tenor range, or extending it by going into falsetto; or a church singer singing the alto lines falsetto, as they do in cathedrals today.

Driven offstage by the coming of the castrati, the countertenor voice was confined to churches for the ensuing three centuries, and was reclaimed only when Michael Tippett heard Alfred Deller humbly singing in Canterbury cathedral. "In that moment, the centuries rolled back," said the composer, who went on to launch him as a concert artist. And when Benjamin Britten wrote A Midsummer Night's Dream as a vehicle for Deller's voice, that roll back began in earnest. Deller's voice had ethereal beauty, but he couldn't act to save his life: when the charismatic, clarion-toned James Bowman took over his role as Britten's Oberon, the countertenor voice came into its own, and countertenor stars began to proliferate, with their voices coming in all shapes and sizes. At one end of the spectrum was David Daniels, an American with a luxuriously feminine sensuality of tone; at the other end was Andreas Scholl, a Clark Kent lookalike from Wiesbaden, whose sound has a heart-stopping purity.

Each year brings its crop of new stars, but the one currently making the operatic running – and carrying off the Royal Philharmonic Society's 2010 Young Artist award – is 31-year-old Iestyn Davies. Yet countertenor fame was initially not on his agenda. Encouraged to learn the piano and recorder from a very early age, he entered the choir at St John's, Cambridge, when he was eight. At that time his vocal hero was Aled Jones, whose rendition of "How Beautiful are the Feet" he faithfully reproduced for his audition. In those days, he says, he tended to daydream: "One day when I forgot my solo entry, the choirmaster hissed in front of everybody that he would never give me a solo again." It seems his talent forced the choirmaster to relent.

At 13, he was selected as a treble Cupid for a stylish commercial recording of Henry Purcell's Timon of Athens, but at that point he was more interested in trying to become the new Damon Albarn in a pop band for which he wrote the songs and accompanied them on guitar; his voice, he says, was a "hammy pop tenor", and they almost got signed by Sony. "But at the back of my mind I always had this pride at having been a treble soloist in a good choir. And that always felt like home."

His countertenor career began at Wells Cathedral School when he was 16, and entirely by accident. "I was sitting there in choir rehearsal as a bass, a bit bored, and I started singing falsetto because it felt quite nice. It didn't work particularly well, but the feeling reminded me of what it was like to be the treble soloist. Somebody next to me said it sounded OK, and suggested I offer myself to the Wells Cathedral choir." He did so, and was invited to bolster them as an unpaid "dep" once a week. That was an apprenticeship of sorts, he says, both daunting and wonderful. "My range was appalling; so was my stamina. And I had this typical countertenor thing of seeing the high and low notes coming, and panicking in advance." He decided to get some training: "I knew that if I could get my voice right, everything else would fall into place. My musicianship was fine."

He went back to St John's as an undergraduate choral scholar, where he gave his countertenor solos to a friend because he still didn't have the nerve to sing them himself. Finally, he found a tutor who showed him the key to good breathing, on which all singing depends. "It's like the high jump, or changing from 100 metres to 400 metres – a different muscle. There's no mystery to it." Scholl embodies his vocal ideal, "creating a column of sound which doesn't weaken, and stays absolutely even". This is actually a good description of Davies' own sound, which Bowman – doyen among countertenors – has hailed as beyond compare.

But the world into which Davies has catapulted himself is still dominated by the ghosts of the castrati, whose weird vocal abilities determined the music which today's countertenors must sing. As the countertenor chronicler Nicholas Clapton points out, pre-pubertal castration prevented the larynx from growing: the castrato's vocal cords were thus smaller and finer-textured than those of an adult male – more like a female soprano's, in fact. And with this soft and flexible apparatus, the singer could perform exceptional vocal acrobatics. Moreover, as there was no testosterone in the body in adolescence, the joints between the bones didn't harden, the bones kept growing, and the ribs kept growing too. With unusually big chest cavities, the castrati could take in more air – hence the impression that they could sing for ever. Their amorous exploits – highly sexed but safely unable to procreate – completed the picture: no wonder they were the pop stars of their day.

And it is in the footsteps of these exotic creatures that Davies is currently treading, with the British premiere – 322 years late – of Agostino Steffani's Niobe at Covent Garden. Opera by opera, the original castrato repertoire, which now belongs by right to the countertenors, is being reclaimed from the basses, tenors and women who for centuries have colonised it, and what is being revealed is fascinating. The coloratura-fuelled role Davies sings in this tale from Ovid gives ample scope for his talents: "It's all about the abuse of power, and I end up being the last man standing. In my final aria I sing 'Crown me and applaud me' as the other characters die and turn to stone." This sort of moment, he adds with a laugh, is every countertenor's dream.

One thing for which he has needed no lessons is physical comedy, for which his gift seems inborn. "Part of me," he says, "would love to be Rowan Atkinson." It was this part which made him capitalise on an accidental fall on a flight of stairs in the English National Opera production of Handel's Jephtha. Playing the mournful, droopy Armindo, he turned this fall into a brilliant piece of business, which brought the house down every night; and his comic performance in the ENO Partenope lit up the stage whenever he appeared.

"I am increasingly coming to feel that what audiences respond to in a singer is personality rather than technical perfection," he says. "The voice is the one instrument which is truly you." But in his case, the body counts too.

Earlier this month, Davies released his debut CD on the Wigmore Hall Live label – a collection of Baroque elegies and arias in which he is accompanied by the Guadagni period ensemble. Meanwhile, the Wigmore has bestowed on him the accolade of a residency for next year – the first it has ever given to a countertenor. According to the Wigmore's director, John Gilhooly, who closely monitors the habits of his audiences, countertenors bring in an unusually youthful crowd.

Asked for his take on this, Davies ruminates: "I suppose it's connected with the fact that there are still not many of us. And there's always that mythical quality about a man singing in a high voice. It's an outsider thing, and young people like to associate themselves with that; it's like a club. A few months ago I was at a David Daniels concert, and I felt as though I was the only straight man in the Barbican. It was a bit like being in a gay sauna, full of couples, but with different music." OK, he's exaggerating, but not much. But this remains an outsider art whose appeal transcends all considerations of sex and gender.

'Niobe' is in repertory at the Royal Opera House, London WC2 (tel: 020 7240 1200, roh.org.uk), until 3 October

Hitting the heights: How Farinelli took castrato singing to another level

Farinelli (1705-1782, right) was the greatest of the castrati, even bewitching his rivals with his spell. Sharing the stage with him was the equally famous Senesino – who in one opera was supposed to be playing an evil tyrant but ended up totally forgetting his fictional character, and embracing Farinelli in adoration.

Imitating birdsong was an art which castrati had to master, and they were often set to duel with instrumentalists. While still a boy in Naples, Farinelli was matched with a trumpeter who took the contest to such heights of virtuosity that people assumed Farinelli was trounced. Then, said a spectator, “With a smile on his countenance, showing he had only been sporting all that time, Farinelli not only swelled and shook the note, but ran the most rapid and difficult divisions, and was at last only silenced by the acclamations of the audience.”

On the other hand, he was a wooden actor: one critic likened him to a calf roused from its slumber in St James’s Park by the dainty foot of a milkmaid – standing with one hand across his ample bosom and the other on a hip, and occasionally simply reversing the position of his hands.

The castrati were finally driven out of business not by public horror at the necessary mutilation, but by the new breed of macho tenors in the early 19th century. The last castrato – Alessandro Moreschi, known as the Angel of Rome – died in 1922, leaving 17 recordings for us to ponder.

Nicholas Clapton, who has written his biography, hopes some musically gifted manipulator of computer software will attempt a digital reconstruction of how Moreschi might have sounded in the “Miserere”he often sang but never recorded. But it’s unlikely that Italian opera houses will once again resound to the ecstatic cry, “Long live the knife!”. MC