Long day's journey into light

Glyndebourne's first Wagnerian outing introduces soprano Nina Stemme to the 19th century

It's taken Glyndebourne 69 years to get round to doing Wagner, so there's a lot riding on its production of Tristan und Isolde, which opens the season next Monday. Despite what the audio-purists say, casting is all.

As director Nikolaus Lehnhoff observes, the more mature women who normally play the lead are simply not believable: "The lovers must look like lovers. I wanted a child-woman in the grip of an idée fixe, who is on a long day's journey into night. And, in Nina Stemme, I've found exactly that."

Taking a break from rehearsals for her marathon performance, this Stockholm soprano offers a quick resumé of her own long day's journey, a path that has brought her to this key professional moment. A singing career, she reveals, was not her first ambition: "I wanted to be an engineer, but I was sent to a school where each class had its own choir. And that gave me such a sore throat I decided I'd better get voice lessons, to find out if I could sustain things for longer than 10 minutes. I had no ulterior motive – I just wanted to repair my voice." Back then, the voice wasn't even soprano – Stemme had a low voice (she still does when she speaks) and was placed among the altos.

She studied economics at university, but music wouldn't leave her alone: a talented viola player, she once considered making a career out of that. "But after surprising myself by doing well in a choral competition in America, I realised something had been triggered in me. I started to attend the Stockholm Opera Studio, where I discovered the importance of getting a free voice." Free? "Well, in the beginning, I had no top at all, I couldn't get the high note in Cherubino's aria of universal love [from Mozart's The Marriage of Figaro], and the process of freeing up my voice took several years. But I still regarded myself as an amateur."

Then, in what Stemme describes as "an act of pure will", she raised her range from mezzo to soprano, learned a whole new repertoire, and, at her third audition, got a place at Stockholm's National College of Opera, where she finally accepted that it was her destiny to sing. Mozart was her first port of call, but now that she's moved on to Wagner, that 18th-century lightness is vocally out of bounds. "I still adore Mozart, but I can't do him justice any more."

For now, doing justice to Wagner is job enough. "The musical language is difficult to learn – I used literally to become dizzy when I was studying the way the harmonies go in the second act [of Tristan]."

It's not only that the rigours of Wagner place significant physical demands on his performers: in this production, Stemme must seem to float through a giant stepped spiral, wearing an unyielding fibre optic costume. "It's vital to wear sensible shoes." Even amid the glamour of Glyndebourne, it seems, some of the prosaic must fall.

'Tristan und Isolde' opens Glyndebourne on Monday (01273 813813; www.glyndebourne.com) and is in rep to 4 Jul; the season continues to 31 Aug