Sound check: Dance diva's old school sound

Then I found out that you have to do maths anyway," says Katy B. It doesn't sound as though the Peckham singer had particularly go-getting reasons for an impressive education that this week earned her a Mercury Prize nomination alongside her student contemporaries James Blake and Adele.

Talking to me the morning after she heard the news, she confesses that she opted to follow her stint at Croydon's famous performing arts school with a music degree at Goldsmiths College, alma mater of three-quarters of Blur and most of the major British artists of the past 20 years, because it was "literally around the corner from my house".

The red-haired 22-year-old, otherwise known as Kathleen Brien, made her name in the underground dance scene when her early material was enthusiastically endorsed by renowned pirate radio station Rinse, now a legitimate FM operation. It's a world of tower- block broadcasts and small-hours club nights, not a place where qualifications and certificates would matter much, but she earned them even so.

She started at 14 at the BRIT school, whose list of alumni glitters more brightly every year. Amy Winehouse, Katie Melua and Leona Lewis all spent time at the institution that is funded by the British music industry. Adele was in the year ahead of her, more a friend of her friends' older siblings, but Katy was invited to her 18th birthday party. She also saw Jessie J, another future star in the year above, perform an early show in a tiny Croydon club. "She did a Lauryn Hill song and I was blown away. Her voice
is incredible," she tells me.

Katy B left at 18 with a BTEC in Music and her debut album already begun, with Geeneus, the boss at Rinse, producing. It was slow going, however, while Geeneus and his musical partner DJ Zinc worked on other things.

Encouraged by her teachers and her parents to go on to university and not keen on the idea of "getting a job that I'd hate while I finish the album", she chose Goldsmiths to study while holding down a Saturday job in Brixton's JD Sports and spending the £40 she earned every week at the pioneering dubstep club night FWD>> in Shoreditch.

Alongside her Goldsmiths classmate James Blake, who was always on the piano and putting on club nights as a member of the university's Bass Society, she learned the theory of music as well as refining her skills as a vocalist. "I learned about harmony, time signatures. It's really helped me when I need to explain to other musicians how I want a track to sound."

However, she also extols the virtues of the university of life. In the course of her studies she had to write a 3,000-word essay on the origins of "UK funky", the sprightly dance sub-genre that is the female-friendly flipside of dubstep's glowering dark bass. Meanwhile she was becoming the scene's queen, adding soulful but unfussy vocals to tracks by various Rinse-associated producers.

"I've mainly found my path through people I've met outside of university," she says. "You can study to be a singer, but if you don't put in the work outside as well, it's not going to happen for you."

Her impeccable connections extend to dubstep supergroup Magnetic Man, whose single Perfect Stranger reached the top 20 with the help of her smooth voice. Magnetic Man's Benga also produced her signature tune, Katy on a Mission, a number five hit in August last year and easily one of the greatest pop songs of 2010. With its buzzing bass and hummable "who-oh-oh-oh-oh" chorus, it had underground credibility and a big enough tune for everyone to enjoy.

"We were just making it for the clubs. We didn't even think it would get in the top 40," she says of the independently released song that earned her a major label record deal with Columbia. "It was a bit of a shock."

Her debut album, On a Mission, appeared in April and produced more top 10 hits in Broken Record and Lights On, a duet with a resurgent past Mercury winner, Ms Dynamite. "It's been great to have her around, when so much of my time is spent with DJ and producer blokes. I haven't had a chance to talk to her about the Mercury yet but I really value her advice. I pay homage to her every chance I get."

On a Mission is exactly the kind of credible, accessible dance album that the Mercury panel adores, with electronic styles that could only have been made this year but melodies that will last much longer. As is her likeable, unassuming way, Katy B is just happy to be included.

"All my friends and family took over the bar at the Roundhouse after my gig there on Tuesday night, and that felt like my victory party," she says. "I don't think it'll be the end of the world if I don't win." She knows she's in exalted company, but she has the qualifications to prove that she worked more than hard enough to be there.

On a Mission is out now on Rinse/Columbia. Katy B plays O2 Shepherd's Bush Empire, W12 (0844 477 2000, o2shepherdsbushempire.co.uk)
Oct 24-25, and the Mercury Prize winner will be announced on September 6