The X factor: Marin Alsop

Conducting, says the violinist Pinchas Zukerman, who has done it periodically, "must be the most extraordinary profession. Think about it: you're the only person on stage who is facing the wrong way. And how much does the orchestra need you? Very little." The conductor is, in other words, a charlatan.

But the converse view, just as widely held, is that the conductor is a magician. A former Berlin Philharmonic timpanist recalls being immersed in a book when his services were not required, and being suddenly aware that the orchestra's sound had changed. "The rehearsal conductor was doing nothing special. Then Wilhelm Furtwangler walked in: this unbelievable sound was the automatic result. A person who carries the sound so strongly in himself that he brings it out of others, is the most beautiful thing an orchestra can experience."

And then there's this question. "How is it," asks Marin Alsop, "that five conductors can do the same piece of music, and each time it sounds different? I think the answer is that conducting is a metaphor for who you are; it's your essence which directs things. That's what's so special about it."

What's special about Alsop is that she's the only woman who routinely conducts major symphony orchestras: Jane Glover, Emmanuelle Haim et al may be excellent, but they do period work, not the big stuff. Named conductor of the year by the Royal Philharmonic Society in 2002, this forthright American has since amply justified that gong: as principal conductor of the Bournemouth Symphony Orchestra, musical director-designate of the Baltimore Symphony Orchestra, recent winner of the RPS-Radio 3 Listeners' Award, and cutter of a steady stream of award-winning discs for Naxos, she's built a solid musical power base. And as a feminist mover and shaker, she belongs in that stellar league where Davos invites and Time magazine accolades rain thick and fast.

She is shortly to conduct at the City of London Festival, I caught her conducting at the Concertgebouw, in Amsterdam, where the last female to occupy the podium did so 96 years ago. From the moment Alsop bounds on stage in her trademark grey suit with scarlet cuffs and collar, the packed auditorium is galvanised; giving back the energy she has been visibly drawing from the audience, she looks as though she'd happily go on conducting all night.

This, she tells me the next morning, is how she forged the bond that led to her being chosen as principal guest conductor of the Scottish National Orchestra, and later at Bournemouth: "For some reason the musicians wanted me." But that wasn't so at Baltimore last year, was it? A rueful laugh: "Absolutely not." In one of the biggest bust-ups in recent orchestral history, the Baltimore players reacted to news of her appointment with outright revolt. With the wounds so fresh, she's hitherto resisted invitations to talk about it, but today she will.

"I'd guested there eight or 10 times," she says, "and we had a great rapport. The local press leaking the story that I was going to be offered the job was the trigger - the musicians came out and said, 'We want the search to continue'. I thought, uh-oh. It was like being in a slow-motion car accident, as I'd said to the board that I'd take it. I wanted to run for the hills. But then I thought what a message to send to all the other women in the business - the going gets hot and I run. So I had no choice. I told the board I wouldn't accept it until I'd had a private meeting with the musicians, who were astonished when I just turned up."

She won't say what was said at that meeting, beyond the fact that she laid out a quick artistic plan, said how aggrieved she felt by their behaviour and that she wasn't prepared to work with them if they weren't prepared to work with her. 'They had a tough history with their management, and I realised I'd got caught in the crossfire. I hadn't even time to get off the stage before they apologised and asked me back. From a start like that - starting your marriage with a divorce - the only way on is up. It was stressful, but it made me realise that in this work being liked is not important. My job is to make top-quality music, and to make an orchestra successful. Now my concerts are sold out in Baltimore - maybe because people think they'll see another fight."

She's been a fighter since she went to a Leonard Bernstein concert at nine. "What I registered was his joy, his bottomless enthusiasm, his energy, the sense that he was hugging the audience - I instantly knew what I wanted to do." She'd been playing the violin in an orchestra since she was seven, and had persuaded her father - who now makes her batons - to buy her miniature scores, so that she could get the whole picture. "I was curious about how everything fitted together and who did what when."

As a teenager, she routinely got friends to join her in quintet versions of Mozart symphonies, and when she went to study at the Juilliard she made three attempts to join the conducting programme. After her third failure, she decided to set up her own orchestra, which, by specialising in reviving forgotten American gems, became a runaway success. She owes her conducting skills to persuading everyone who conducted her to give her a lesson, or at least a few tips.

Now she teaches it. The commonest error musicians make when they move from playing to conducting is to assume there's no real technique involved, she says. "And compared with playing the violin - the athleticism involved in becoming an international instrumentalist is supreme - there isn't much. But tremendous physical skill is required to be a conductor too - you can't just get up on the podium and assume you've got it. It's all about body language, and it's not a matter of just keeping time."

The spate of articles about Alsop "poking her baton through the glass ceiling" has now died down, but the gender issue remains her prime concern. She observes with pained surprise that there are no more women conductors now than there were when she started 20 years ago. She's inaugurated a scheme whereby young female conductors can shadow her as she goes about her work, and she's donating most of a large cash prize she recently won to help finance their studies.

She admits that sexist prejudice may always run deep. "If I'm aggressive, people sometimes say it's over the top. If a male conductor is aggressive, he's often praised for his strength. What I aim for, and try to inculcate in my students, is strength without any adjective associated with it. We must de-genderise conducting. This applies to male conductors too, if they want to be truly great."

'Independent readers' can buy two tickets for the price of one to see Marin Alsop conduct the 'Requiem' by Gabriel Fauré on 13 July, 8pm, at St Paul's Cathedral, London EC4. Ticket prices start at £10. Call 08451 207 502 and quote "Independent offer". Subject to availability.