He was the shyly obsessive miller boy of Schubert's song-cycle Die Schone Mullerin - everybody's favourite Lieder recording of 1996. He sounded the part. He grew up before our ears, infatuation turning to desire turning to obsession turning to disillusionment. The detail in his singing was simply astonishing. Had we also seen him, his expressive face and willowy frame would further have suspended disbelief. In David Alden's controversial Channel 4 film of Schubert's Winterreise (Winter Journey), he stalked our imaginations as the poet stalking the winter of his despair. As Peter Quint in Deborah Warner's acclaimed Royal Opera staging of Benjamin Britten's The Turn of the Screw, he found a way of moving through the action that was neither quite spirit nor flesh. On the concert platform or stage, he is an ethereal presence: not quite there physically; all there intellectually.
There's still something slightly incongruous about Ian Bostridge, as if the body were made bespoke for an academic and only later adapted for a stage performer. But it is a quality that he can, and does, use to his advantage. As for intellect, the brainless tenor cliche was never going to apply here. Indeed, it was a close call at one point as to whether Bostridge would take the path of writer and academic (his doctoral thesis, Witchcraft and its Transformations c1650 to c1770, was revised as a book - so now you know why he spooks you) or make a profession of his pastime, singing.
In the event, he never really had to choose between words and music: he opted for them both. There were adjustments to be made, techniques to be initiated and developed. He had no formal training, only basic singing lessons, to sustain him. As if to reaffirm that he was a scholar first and a singer second, he tended to sing "from the neck upwards". He needed to engage his body, learn to breathe, exercise muscles he never knew he had. In short, his athletic mind advised his sedentary body that it had some catching up to do. And if the decorum of the recital platform was not so far removed from halls of academia at Corpus Christi, Oxford, the operatic stage would prove much more of a stretch.
But Bostridge has come a long way in the three or so years since he effectively gave up the day job. From feeling like he was "undergoing remedial therapy for the terminally wooden", his stage work has come on in leaps and bounds. He's looking to do a couple of operas a year: Mozart, Monteverdi, Tom Rakewell in Stravinsky's The Rake's Progress (who might, if he were Bostridge, sell his soul to sing Siegfried). When we meet, he is tentatively feeling his way through rehearsals for Francesca Zambello's new production of Smetana's The Bartered Bride. At least, as Vasek, the opera's enchantingly silly and transparently guileless dupe, he is: tentative is as self-assured as Vasek gets. He stutters his way through comic arias marked "lamentoso". He is gangly and inarticulate. Bostridge is working on the inarticulate.
The "not knowing what to do with your hands" stage is behind him now (though Vasek might disagree). Directors such as David Alden and Deborah Warner have, in their very different ways, unknotted the inhibitions in him. Their trust has been his undoing, so to speak. Alden - whose highly expressionistic, "operatic" way has always courted controversy - urged him to tap into the emotional energy of a piece by pushing at the physical extremes. Warner, on the other hand, encouraged him simply to "claim his space", be himself and use himself to create someone else. "Deborah isn't interested in actors putting on characters like costumes," says Bostridge. "She's interested in keeping the rehearsal process alive in performance, in keeping the possibilities open. She always maintained that if you could precisely define a moment, then it was theatrically dead. And that was a revelation for someone like me who was apt to analyse everything to death."
The Warner/Bostridge partnership is set to continue with a "staging" of Janacek's dramatic song-cycle The Diary of One Who Disappeared in a new translation by Seamus Heaney (to be seen in London, Paris, and New York). Warner's experience with Fiona Shaw in TS Eliot's The Waste Land fuelled her fascination for the theatrical potential of narrative poetry.
But taking Alden's experiment with Winterreise as a guide, how theatrical, how public, is it possible to be with works whose potency is in their privacy, their inwardness? Bostridge cites the baritone Lieder singer Dietrich Fischer-Dieskau's remark that he considered it "almost impertinent to sing Winterreise in public". "I rejected that view as pretentious gobbledygook," says Bostridge, "until I tried performing it to a paying audience that included my own father. I felt strangely embarrassed. There was an element of voyeurism about the whole experience. But that's what's fascinating about a work like Winterreise: it's this incredibly delicate balance between self-indulgence and objectivity. There's an edge to Muller's poetry, an ability to pull back from itself, to turn self-pity into self-mocking. Without the black humour, cynicism, irony - and you, the performer, have to ensure that it's there - you're left with a long, boring `winter moan'." Or perhaps, for a tenor, that should be "winter whine". Bostridge sometimes wishes he were a baritone: "It's much closer to speaking, and therefore much easier to carry the words..."
And the words - pointed, enriched, elevated, by the "rightness" of the musical line - are everything. Which raises the question of recording. Bostridge has a healthy respect for it. And he has a good contract with EMI which, he claims, buys him generous, unharassed session time. Pressure is the enemy. What he strives for in a recording is not even achievable in singer-friendly venues such as London's Wigmore Hall. It has to do with "returning the music to the domestic sphere where it originated", re-creating that real sense of drawing-room intimacy, or even of someone "whispering in your ear". It's an opportunity to re-imagine works, provided, says Bostridge, you remember that records are made to be repeated. "You have to be aware of that. You might be less inclined to risk those moments in the concert hall where you depart from the sung line to achieve a declamatory effect. Similarly, you might be less inclined to use intonation to create weird flattenings or sharpenings of pitch for expressive effect. That kind of thing can pall with repetition."
Bostridge's voice does not. But it is possessed of a peculiarly "English" demeanour and that provokes allergic reactions in some. Words like "prim" and "precious" are bandied about by those who find it hard, if not impossible, to get beyond the distinctive colour of the sound. The French are sniffy about his German lied; the Germans think it's the cat's whiskers. Bostridge is philosophical. It's the only voice he has: he can't change it; he doesn't despise it. He raises the spectre of Peter Pears, a resourceful singer who was increasingly at odds with his idiosyncratic - and much-maligned - voice. And yet it was that voice on which Benjamin Britten tailored some of this century's greatest song writing.
Bostridge is in no doubt about that (his already substantial Britten discography bears it out). Or indeed of the ferocious technical difficulties that sat so well for Pears (around E-F-Fsharp, the part of the voice that most tenors want to avoid) but for nobody else. Which is why when we hear Britten we hear Pears, and when we hear Pears we hear Dudley Moore (remember Beyond the Fringe?). Bostridge tells of a Pears masterclass in which he instructed a young tenor in the colouring of an extremely difficult phrase from Britten's Winter Words: "More yowl," he urged, "More y-o-w-l."
Happily, Bostridge is, as yet, a yowl-free zone.
The Royal Opera's `Bartered Bride' opens at 7pm tonight, then runs in rep with Rimsky-Korsakov's `The Golden Cockerel' to 14 Jan, at Sadler's Wells Theatre, Rosebery Avenue, London EC1 (0171-863 8000). The 19 Dec is broadcast live on BBC2 and Radio 3Reuse content