Obscure novelists can suddenly win a prize; pop singers can have a hit at 40; but with opera singers, it's different: stars tend to be spotted early, or not at all. The Korean soprano Hyunah Yu, however, was unknown on these shores until the maverick director Peter Sellars made her the lead in his anti-slavery version of Mozart's Zaide at the Barbican, in London, this year. And her lustrous presence and purity of tone were not the only reason she illuminated the stage: playing an innocent victim striking a blow for freedom, she exuded a uniquely vulnerable spirituality. Where had she been, and why had we not heard of her before?
The short answer is that, although she had recently become known on the American conservatoire circuit, before that she wasn't a singer at all - she was a geneticist. The precipitating factor in this career change was a story of shocking tabloid luridness: to hear that story at first hand, and to see how it fed into such sublime art, I met her during a rehearsal break at the Barbican. Treat her gently, I'd been instructed, let her tell you what she wants, at her own pace.
The lithe beauty who bounds in to greet me could have come straight from the gym, and yes, gyms feature prominently in her regime: the set that she had recently had to scale in Vienna had been a vertical wall, and anyway, she's keen to stave off old age. So - life-story, please, and she's off, talking about Seoul, where she spent her first 13 years, before her Presbyterian pastor father decided to transplant his wife and their five children to Charlottesville, Virginia. What year was that? She prevaricates. OK, when was she born? "April." But she won't say which April. After a few more clues, I work out that she must be an incredible 37. Divas don't often launch this late.
"My father was a Renaissance man," says Hyunah. "He majored in philosophy, but knew about everything, and classical music was his first love. He put speakers in our rooms and piped music through them, so we woke up to it and heard it all day. When we came home from school and the music was on, we knew he was home."
She became a successful teenage cellist, played the organ and sang in the church choir, but suddenly decided to become a microbiologist. "I asked God what I should do, and I heard - no, I felt - a voice saying, 'Be my hands', and I realised that that was what doctors were when they healed people - God's hands."
By the time she was 19, she had also enrolled at business school: "I thought, if I put my mind to it, I can do anything - I loved challenges. Naive arrogance!" She pauses, ruefully, then continues her tale. How she met Yeong-Ho Yu, her Korean husband-to-be, at a time when, as "just a selfish go-getter", she "wasn't interested in guys"; how Yeong won her over by his loving persistence, and they became a happy couple with their son Daniel. "Of course, I didn't know I was going to lose Yeong after just one more year."
At which point, she stops, takes a deep breath, then switches to talking about Daniel - how closely he resembles his father, how big and clever he is, and how he recently astonished his teachers by memorising overnight the first 87 digits of a decimal number. Then back, reluctantly, to Yeong and recalling the day tragedy befell them in Philadelphia: "It was a very cold evening, St Valentine's Day. I was in church rehearsing for a concert, and Yeong said that he'd stay outside to nurse one-year-old Daniel in the car. A friend suddenly came in and said that I had to go out, Yeong had been stabbed.
"Outside, the street was full of lights and police cars, and Yeong was lying on the ground. Then I realised the car wasn't there, and a friend asked me, 'Where's Daniel?', and that's when I freaked out."
A pause, and Hyunah goes into medical detail about entry and exit wounds, and why her friends hadn't realised that Yeong had actually been shot three times at point-blank range by a pair of teenage car jackers. She explains how quickly he must have died. "And all that I could say was, 'Daniel was in the car!'.
"Two hours later, a woman rang the police to say that she'd found a baby in an alleyway by a trash bin, with stray dogs nosing round. He had just a blanket on him - he must have been so cold..."
Hyunah says that she lost her mind. "For months after that, I had friends staying with me 24 hours a day, giving me liquids intravenously - I was so dehydrated from crying and not eating. I would be constantly dreaming of meeting Yeong and saying to him, 'My God, I thought you were dead!'. And he would laughingly reassure me that he wasn't.
"It's strange, but only a week before it happened, he had mentioned that he wanted to be buried in Korea, when his time came."
Premonition? "I think so." She flew back with his body. "It was a long time before I could grieve."
It was her pianist sister who set recovery in motion, by suggesting that she audition as a singing student for the Peabody Conservatoire. Her singular talent was immediately spotted, and, shortly afterwards, spotted again by Mitsuko Uchida and the Borletti- Buitoni Trust, who took her under their wing. But she believes that she was recognised as a singer not so much for her technique as for the passion she put into it: "We musicians are nothing but vessels, channels, we're servants of the composer, and our uniqueness - if we have that - resides in our openness.
"My life - and what I went through - led me to find true musical feeling. But at first I could only sing from here" - she points to her throat. "I couldn't sing from down here" - her heart - "because it was just too painful. I would have been too choked to sing. I could do the high coloratura, the surface stuff, but not the low notes."
She was helped over that hurdle by the British baritone John Shirley-Quirk, who was one of her professors. "He had himself been through sadness, and understood. One day, he simply said to me, 'Next time I hear you, I want to hear you sing sad songs'."
In the role of the slave Zaide, she says, she finally came through. "I cried very much while rehearsing: I realised I wanted to share my pain, because no one is exempt from it. It just takes different forms. All life is a struggle, but a beautiful struggle."
More fruits of her personal struggle will be apparent in January, when her debut disc is released. There are arias from Zaide, but the bulk of it is Bach, exquisitely sung. She had been due to star this Christmas in a new opera that John Adams had written for her, but when she discovered that the project had been developed in a way that she found unpalatable, the collaboration was terminated by mutual consent: she may be a neophyte, but she's no pushover.
How much did religion help in getting her through all this? "Music is a gift from God. Through it, anybody can find comfort and strength, whether they are explicitly religious or not. For me, music is God's grace - you don't ask for it, it's given to you. Faith is who I am, but I don't normally spell it out."
Hyunah Yu, Soprano is released in January on EMIReuse content