By Dawn's bright light

Dawn Upshaw hails from Nashville, but she's equally at home at Glyndebourne and on Broadway.

It is 10.30 in the morning. Dawn Upshaw is in London on an away- day from Glyndebourne, a string of interviews in prospect. Not her favourite kind of day. Singing comes naturally, talking about it does not. Nor does talking about herself. That's a first, of course. But put yourself in the journalist's shoes. Imagine returning from Glyndebourne where only moments before, Dawn Upshaw, soprano, went quietly, exquisitely into that sweet night at the close of Peter Sellars's production of Handel's Theodora. On your car radio you catch one of her feisty Broadway renditions - a song by Gershwin, Bernstein, Sondheim, Rodgers and Hart. It isn't the same singer. Well, it is, but somehow you can't reconcile the two. You want to talk to them both.

Which brings us back to 10.30am in a hotel just across the street from the BBC's Broadcasting House. I feel like the warm-up man. But we've done this before, we've graduated from interview to informal chat. Far more revealing. Far more in character. Dawn Upshaw is a singer without airs, without attitude. Her upbringing in Park Forest, Illinois - cosy, middle- America - gave her a good handle on reality. She's never let go of it. Her family (two children and a musicologist husband) provide the continuum. Then there's the work. Or rather, the work process. Ask what really satisfies her about working with Peter Sellars (Theodora is their second collaboration - first came Messiaen's St Francois d'Assise) and she'll tell you that with Sellars it's the feeling that nothing is ever truly finished, that he is constantly reappraising, coming in night after night even mid-run - to give notes. To some, that would be an irritation, an intrusion - a short-cut to their insecurities. But she welcomes it. There's an old saying: it is better to journey than to arrive. Upshaw can relate to that. In a sense she has actively resisted "arriving". Divas "arrive". And Dawn Upshaw is no kind of diva.

So young singers the world over will want to know: what does she know that we don't? Is it really still possible to be selective and successful, to be extra-picky about repertoire, venues, the company you keep, to make your own conditions, maintain your integrity? Dawn Upshaw will more than likely respond with a smile, a shrug, an "I guess". Because the truth is she doesn't know how to answer that question. It's a question about instinct - about knowing. Knowing what works for you, knowing what you're best at, what you can and can't do, knowing how something should go, how it should sound, making that vital connection between the words and the music. How do you explain what just comes naturally? How do you define a quality? It's that quality of "nothing to hide", of honesty, candidness, that draws people into Upshaw's confidence. You take everything she sings personally because it is personal. She's a very bad liar. People trust her. And if that's not the basis for making lots of friends, I don't know what is. You don't have to sing every night of every week in all the right places. But when you sing and what you sing must count for something.

So you are only as good as the choices you make. It helps, of course, if you can mate with a record label (Nonesuch) that not only shares but strives to encourage and promote your penchant for the adventurous, the unusual, the exotic, the offbeat. It all began with an audacious debut album of Barber, Menotti, Stravinsky, and Harbison. A new direction, a new dawn (that's not a pun, that's an occupational hazard): the "themed" recital disc, repertoire chosen not just for itself but for the interesting and often oblique ways in which it interacts. The titles of the sequels - "The Girl with the Orange Lips" (a kind of "Upshaw in the Sky with Diamonds") and "White Moon" - promised, and delivered, more of the same - or rather more that was not the same. Somewhere in there was the Gorecki Third Symphony phenomenon. And two "Broadway" albums, each with their fair share of surprises.

"After hours" at this week's Proms, Upshaw takes her Broadway persona into the Albert Hall for a cabaret entitled Dawn at Dusk (as I say, an occupational hazard). Now for those of you who might be thinking that a major transformation is involved here, the lady herself should put you right. "This is hard. Really, I don't want to duck the question, but I sing so much on instinct that you'd probably do a better job of describing what actually happens yourself. I don't really belt. I think there's only one moment in 'There Won't be Trumpets' on I Wish It So where I do. And even then, it's not a pure belt - it's what I would call a healthy belt! By which I mean that it's a comfortable mix of the head- and chest-voices. In opera or lieder it's rare to sing as low as I do in musical comedy. Because of its popular style, this music was written in a range where more people could comfortably sing it. So again we come back to style. That's what inspires me to sing in a particular way. It's the vernacular of these songs.

"It's almost like speaking. Just the way you adjust the vowel sounds makes all the difference to the colour and articulation. The phrasing comes naturally out of feelings I have for the text. I guess we're back to instinct again..."

We are. The girl from Nashville who once dreamed of being Barbra Streisand or, at the very least, Linda Ronstadt, who imagined that one day she might earn her keep singing jingles, grew into this music. She's never grown out of it. Listen to her in the big second four-bar phrase of Rodgers and Hart's "I Didn't Know What Time It Was", the moment at which the melody makes that leap of faith from popular song into standard. You can hear Upshaw recognise the moment, just from the way she sings it. "Oh yes, you feel the tension in that phrase, the whole tune seems to turn and build upon itself and blossom...". And with that she's off into the middle- eight: "Grand to be alive, to be young, to be mad, to be yours alone..." Again it's the imperative of the words that carries her performance somewhere else. It's the highlight of the album. "So you feel that, too? If only I could have conveyed the same level of connection with every song on the album ... when I hear that track, I realise how far I needed to go with the others..."

Not so far as she might think. But self-criticism, self-effacement, keep her sharp, inquisitive, striving. Her "voice therapist", Joan Lader, continues to work on the theory that it doesn't actually matter what you're singing, that there is a perfect place for each and every note. Meaning that from a technical standpoint, her Handel is coming from exactly the same place as her Richard Rodgers. Really? Yes, really. "I spent most of my training trying to bring my head-voice down as far as I could in order to create a more even sound throughout the range. I'm still working on it. The 'operatic' sound of my head-voice from G above middle-C on down was something that never rang true for me. So in Theodora I'm using my so-called chest-voice a lot. Hopefully it doesn't sound like I'm thrusting it from a different part of my body."

No, but there were moments when I was conscious of her pushing the emotion outside the discipline of Handel's vocal line. It's a point she takes graciously, reminding me once more that in her preoccupation with communicating the text, she sometimes gets "lost in the sound". But working with a Baroque specialist such as Lorraine Hunt has made her think long and hard about the sanctity of line and sound. She marvels at what Hunt can convey through sound alone. And that's not a criticism. It's just never been her way. It's not the beauty of Upshaw's voice (she herself doesn't consider it special) but the intensity that is so affecting. She's with Roger Norrington when he says that "music isn't about sound, it's made with sound. It's about gesture, expression, movement, drama."

Which is why she's always going to be more of a Pamina and a Melisande (one of her few new roles - Salzburg / Paris) than a Sophie. She didn't enjoy the Rosenkavalier experience beyond being "a part of the best bits". Indeed, she'd far sooner get stuck into devising new recital programmes (or variations thereof - a musical theatre evening is currently in discussion for New York) than compromise herself in the opera house. "When I have experiences like Glyndebourne, I think to myself - why do it unless all the pieces fit?" Asked and answered.

n Dawn Upshaw sings American operatic arias and popular song at the Proms, Thursday, 10pm. Booking: 0171-589 8212