'I'm a bit like a rubbish super-hero ..." says Burial, shyly. The underground dubstep producer - whose debut LP was one of last year's critical smashes, and whose second is one of this year's most anticipated - makes the comparison because he leads two lives. The young south-Londoner slips anonymously through normal life, with few knowing that he has a separate musical existence as Burial. Equally, few of those who know him as Burial have any idea of his identity outside music. That means this piece can't give you a potted biography, dwell on his childhood, or tell you what he's been up to for the past year. He won't say.

Burial doesn't do DJ gigs, live performances or radio shows, and only a few photos exist of him, taken by the photographer Georgina Cook, and obscured to conceal his identity. "Only about five people outside of my family know I make tunes, I think. I hope," he says.

Technically, Burial doesn't do interviews, either. Our meeting only comes about after much gentle persuasion and the realignment of our "interview" as a "casual chat about tunes". As I stand in the London drizzle waiting to meet someone I have no chance of recognising, my mind plays tricks. That guy crossing the road who looks like Brad from Neighbours, could that be Burial? Or the wild-eyed Turkish guy on crutches? Or the Japanese guy in the green suit?

When Burial does turn up, he talks with incredible passion and sincerity - and does it so quietly that my Dictaphone barely picks up his voice, making him sound in playback like a ghostly presence. Which is appropriate, because Burial's richly atmospheric music leaves you feeling slightly removed from the tangible world. His debut was clouded in pirate-radio crackle and cassette fuzz, the soundscapes dotted with the sound of rain, fire and distant voices. It became a word-of-mouth sensation far beyond the dubstep scene, appearing on the Guardian music site's "best of the best-ofs" list of albums, aggregated from all the other critics' end-of-year lists. So how did he celebrate, if no one knew he had anything worth celebrating?

"I was never expecting anyone to hear it," Burial says. "I was buzzing, totally buzzing. But I had to hide that feeling, I didn't really have anyone to tell, apart from my brothers and my family - but that was all that mattered to me.

"I like it that way. I've had times when I've had mates sitting next to me and they've put my tunes on without knowing. I would just sit there whispering to myself, 'Please don't put that on - or at least, don't say anything bad about it," he says, with a nervous laugh. "I've had someone say to me, 'Yeah, Burial's a girl. I know someone who met her.'

"It's just the way I am. I can't step up, I want to be in the dark at the back of a club. I don't read press, I don't go on the internet much, I'm just not into it. It's like the lost art of keeping a secret, but it keeps my tunes closer to me and other people."

Burial's privacy stems from a fascination with what he describes as the "dark light" of UK club culture - enjoying music more the less you know about its makers. "I love that with old jungle and garage tunes, when you didn't know anything about them, and nothing was between you and the tunes. I liked the mystery; it was more scary and sexy, the opposite of other music."

His own music, though, isn't really made to be listened to in clubs. "It's more about when you come back from being out somewhere; in a minicab or a night bus, or with someone, or walking home across London late at night, dreamlike, and you've still got the music kind of echoing in you, in your bloodstream, but with real life trying to get in the way. I want it to be like a little sanctuary. It's like that 24-hour stand selling tea on a rainy night, glowing in the dark. It's pretty simple."

He is a romantic about music, and especially about what he sees as the forgotten musics - the urban dance styles of the past couple of decades. He sees dubstep as part of the lineage started by rave in the 1980s, and believes his own music connects directly with the impulse that first sent people to seek out the early raves.

"I'm not old enough to have been to a proper old rave in a warehouse or a field," he says, "but I used to hear these stories about legendary club nights, about driving off into the darkness to raves on the outskirts of London. But it's got this sadness now, because most club culture got commercialised in the 1990s; oftentimes it got taken off ravers and sold back to them. But it's still out there; there's a signal, or a light. It's like there's someone still holding a lighter in a warehouse somewhere."

He snaps out of his reverie with a laugh. "I do think about it like that, though. I don't always like this idea that club music should be this new disposable thing. That's wrong."

Burial's second album, Untrue, is punctuated by the skippy drums and "girl-next-door" vocals of two-step garage and early jungle. Elsewhere, the sounds that make up his night-time sketches are lo-fi - he has only worked in a proper studio a few times in his life, a fact he is mildly embarrassed about. He confesses that his favourite sounds are sampled from "Vin Diesel's car keys in a film, bullet casings hitting concrete in Metal Gear Solid on the PlayStation". Another is the sound of his brother's lighter sparking. Burial's music succeeds because of this warmth, this closeness to real life, which marks it out from the super-produced efforts of certain goliaths of dance music, all clean lines and smooth edges.

But while it is still distinctly DIY, some of the melancholy of Burial's debut has dissipated on this new album, which is more heavily loaded with garage-inflected vocals, and more upbeat as a consequence.

"I don't want to be just bleak," he says. "I wanted to make a glowing, buzzing album, do it really fast; to cheer myself up." He smiles. "I'll do the hi-tech ultra-darkside album next time."

So what is the mood of Untrue? What was Burial doing while he thought about how it should be made? He sums it up: "I would sit around waiting for night to fall, wait for summer to end. Or I would go out, wait for it to get dark, and then I'd go back and work on it, sort of hypnotise myself. I love that feeling when you know that almost everyone in your city is asleep, or you go out and listen to your tunes in someone's car at night. It's like hibernating.

"When I'm awake all night, sometimes I see the people and the city waking up around me. I feel a little bit moody at them for stepping into my night-time. What I want is that feeling when you're in the rain, or a storm. It's a shiver at the edge of your mind, an atmosphere of hearing a sad, distant sound, but it seems closer - like it's just for you. Like hearing rain or a whale-song, a cry in the dark, the far cry."

· Untrue is released on Hyperdub on November 5.