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Brass players used to be easy to spot. You'd just look out for the biggest, burliest blokes propping up the concert hall bar. But 25-year-old trumpeter Tine Thing Helseth is breaking the mould. Later this month she makes her solo debut in a new concerto by Matthias Pintscher at the Proms, a festival she used to watch on television in her native Oslo as a child and always dreamed of performing at. It marks a milestone in an increasingly glittering career that is upending the conventions of the classical music world.

Underneath Helseth’s bubbly blonde exterior lies an obsession with her instrument that began even before she had started to formally learn it (when she was seven) at the feet of her trumpet-playing mum.

“I have a lot of childhood pictures showing me pretending to play the trumpet,” she says. Her passion didn’t waver during her teenage years, partly thanks to her mother stepping down as her teacher. “I love my mum but that would have been terrible.”

The only thing that might have turned her head was football. She lived in the shadow of Oslo’s equivalent of Arsenal, Vålerenga. “But it was never a question. A lot of my friends didn’t know what to do with their lives. But I always had this very strong idea of what I wanted.”

At 18 everything took off. She was runner-up in the Eurovision Young Musicians contest and “suddenly I was travelling around the world being a soloist”. Her school teachers tried to push other possibilities in her direction but she wasn’t interested. “I’ve always been very ambitious,” she admits. “Not in a manic, crazy way but I always wanted to do my best. I think you have to be like that for this strange life.”

The trend for pretty girls flourishing in the classical music business is a live issue. Dame Jenni Murray recently lamented how “sex sells” in the industry. But despite the glamorous CD covers and male-friendly marketing campaigns, Helseth feels far from exploited.

“I’ve heard so many horror stories but my record company, EMI, have been great. They’ve never tried to make me do anything I don’t want to do. We’ve always been on the same page,” she says with a smile. “So far.”

But then Helseth is a dream for any record label. She’s open to collaborating with other musical worlds (she has a jazz quintet, for example) and comfortable segueing from the academically serious to the commercially Classic FM. And her talent is extraordinary. Her ability to transform the brassy trumpet sound into something soft, supple, lyrical and delectable needs to be heard to be believed.

She is always on the lookout for fresh ideas to put a spin on her work. “An orchestra has a trumpet soloist once every five years. Whereas they have a violinist every week practically,” she sighs. “So you have to make your career a bit different.”

Helseth is constantly commissioning and rehearsing new pieces. “I had six new concertos to learn in the first three months of this year. It was a bit much,” she says with a look of exhaustion in her face. “I won’t do that again.”

Burnout is all too common among young virtuosi such as Helseth. To navigate this tough, treacherous and often lonely path, she has a sister in arms, violinist Nicola Benedetti, another supremely gifted and confidently broadminded musician who is both critically respected and popularly adored.

“It’s great to talk to someone who is in exactly the same position and the same age as me. We have a lot in common,” she admits. “And I like how she does things.”

Like Benedetti, she has a number of fingers in different pies, including a musical foothold in Oslo. I was there for her inaugural Tine@Munch music festival, which takes place in the Munch Museum in the leafy suburbs but will move to the museum’s flash new home on the city’s shoreline in 2014. For the moment, the festival retains a family feel: it lies a stone’s throw from where Helseth grew up and the volunteers are all her old school friends.

And there’s the added security of Ten Thing, the all-female brass ensemble which she started when she was 20, who meet up four or five times a year. On Monday the twenty- and thirtysomethings performed a new work by British composer Diana Burrell and put their own twist on tangos, seguidillas and serenades by Grieg, Piazzolla and Bizet as part of their chamber Prom at Cadogan Hall. They began as strangers but are now close friends. “Intense” trips, cooped up in bunk beds on tour buses, cemented their friendship and taught them valuable lessons — “if someone wants to be alone let them be alone”.

Helseth is now air-bound most of the year, such is the demand for her. “I’m away 250 days a year and play around 100 or 120 concerts,” she says, “and of course it’s never like a holiday: you still have to answer your emails and call your friends. You have to make it work so it doesn’t feel like you’re waiting to come back to the real world.”

Only a handful of trumpeters ever gets to achieve what Helseth has managed to achieve. I point out that the star trumpet soloist appears only once in a generation. “I can’t think too much about that, it’s too big a thing,” she says.

“I never had to ask myself if this was something I wanted to do, it’s just how it always was.”

Tine Thing Helseth performs at Prom 48: Ravel, Matthias Pintscher and Stravinsky at the Albert Hall, SW7 (0845 401 5040, bbc.co.uk/proms) on August 18.

The Proms run until September 7.