Half a century ago, the countertenor was an endangered species, surviving only in the ranks of English cathedral choirs. The early music revival, especially the rediscovery of baroque opera, changed all that, bringing to light vast quantities of music written for that even more exotic voice type, the castrato. Given that the castration of pre-pubescent boys for purely aesthetic purposes was no longer considered acceptable, these parts were initially transposed down for lower male voices or sung by women.

Gradually countertenors also moved in on this repertoire and the public appetite for the voice soared. Given the current popularity of baroque music and Handel's operas in particular, it's no coincidence that two of the biggest singing stars of the moment, David Daniels and Andreas Scholl, are both countertenors.

The English choral tradition no longer has a monopoly on producing countertenors as it did in the early days of the baroque revival - Daniels and Scholl are American and German respectively - but it is still the route by which many countertenors learn their craft. Of the up and coming generation, Iestyn Davies is the pick of the bunch.

Still only in his late 20s, he has already established his reputation in the opera houses and concert halls of the UK and Europe. He made his Scottish debut two years ago singing the role of Joad in the Scottish Chamber Orchestra's performance of the little-known Handel oratorio Athalia, where the beauty and easy fluidity of his voice made quite an impression, one subsequently reinforced by several Bach performances in Perth with Concerto Caledonia. Scottish audiences can hear him again as he returns to the SCO, to sing the role of Didymus in Handel's Theodora.

Davies is from a musical family; his cellist father was a founder member of the Fitzwilliam Quartet, the ensemble that Shostakovich entrusted with the first western performances of his last three string quartets in the 1970s. Davies junior studied cello with his father, and at the age of eight, became a chorister at St John's College Cambridge.

"That experience really got me into singing; everything I learned came from there," he says. "We were singing every single day, touring and recording. It's basically the same job I do now, but you're a child, which makes it very interesting; of course it gets stuck in the blood."

Davies spent five years at St John's as a chorister and later returned as an undergraduate. Between these two stints at Cambridge, he attended the specialist music school at Wells Cathedral, though it was only towards the end of his time there that he made the transition to singing countertenor.

Biographies of well-known countertenors - particularly the flamboyant American kind - are full of anecdotes of how they discovered their true voices doing impressions of the great sopranos at parties. For Davies the realisation was rather less dramatic.

"When your voice breaks, the last thing you think about is staying up in the treble register by singing falsetto," he says. "My natural speaking voice is bass so I ended up singing that in the school chapel choir. Then, when I was about 17, I got a bit bored and started singing alto in the choir, just quietly in the background during rehearsals and it just seemed to feel quite comfortable, though it wasn't a completely filled-out voice - I didn't have the range I do now."

To begin with he knew little about the repertoire of any of the great countertenors of the day. "When I was about 18 the head of composition gave me a CD of Andreas Scholl singing Bach Cantatas. The first time I played it I actually thought that sounds pretty average'. Of course, when I actually got to know the sound I grew to love it. That got me listening to the repertoire but it came after the voice. I was lucky because I wasn't obsessed with trying to impersonate anybody or desperate to sing a certain role."

In terms of vocal range, Davies is a classic male alto along the lines of Scholl. "Someone like David Daniels, who started off as a tenor, has a much higher voice," he says. "I wouldn't be comfortable singing a lot of the repertoire he sings, but anything Handel wrote for Senesino fits me fine." Since the famous castrato created 17 principals roles for Handel, including Julius Caesar, Davies has plenty of material to work with.

Early on, Davies decided that he was going to sing opera. "I think I always wanted to be a solo singer and as I discovered the repertoire I realised that was going to be the way to go."

After Cambridge he did the opera course at the Royal Academy of Music. But the decisive moment in his career was when he came second and won the audience prize at the 2004 London Handel Competition. "I got an agent, and then doors started opening for auditions."

Davies has discovered that performing opera can be a frustrating experience. "You don't tend to sing much when you're rehearsing so you can find yourself really losing stamina, whereas concert work keeps you on your toes. I'm trying to do about two operas a year, which works out at about a third of the year, and the rest of the time is spent doing concerts - I'm doing more modern repertoire now - and resting."

What he does now is likely to impact on the longevity of his career. "There's always the question of how long you can continue singing as a countertenor because the voice sounds really fragile," he says. "Tenors are often still going strong in their 60s but countertenors tend to dip before then. I think it's all to do with how you look after your voice and not doing anything stupid.

"You can end up being a real diva, constantly drinking water and going to bed early," he admits, "but I think it's worth it."

  • The Scottish Chamber Orchestra perform Theodora at the Queen's Hall, Edinburgh, tonight and City Halls, Glasgow, on Friday.