In Jeff Jank's loopy, cut'n'paste mind, Quasimoto is a Kool Aid-red space alien with pointy ears like a squirrel, a big-assed snout halfway between a hippo and a pig, a doobie perma-glued to his sneering lip, his eyes heavy-liddedly gazing at the ass that passes his brownstone palace of paranoia. Across Jank's sleeve artwork of Quasimoto's two albums to date, 2000's The Unseen and this year's The Further Adventures Of Lord Quas, the luminous blob nonchalantly tosses demo tapes out the window of a speeding motorcar, his victim tied helplessly between the fins on the trunk; sprays graffiti on a wall while dressed like a member of Run DMC; splits a 40 and a spliff with his producer Madlib in the back of a grotty taxi; stabs an enemy in the spine with a trident after bashing his face in with a brick and/or hammer; and stares up the skirt of a young girl, gazing blankly at her white-pantied undercarriage.

You've got to forgive Jank. Quasimoto's music stirs up such visions, a rich and shimmering mess of twisted samples and tweaked verses that pieces together a virulently alive caricature of the mean streets of America. Through Quasirnoto's verses stroll winos and street people, whores and pimps, criminals and their victims. Laced with dope paranoia, it's a colourful and profane nightmare, all-consuming and overwhelming, hilarious and terrifying, bleak and strangely affectionate.

It's like plugging into the lurid world of Corky McCoy, whose psychedelic street paintings housed Miles Davis' On The Corner albums, and who helped translate Bill Cosby's Fat Albert character for Saturday Morning Cartoons – and wouldn't Quas make a fine subject for a show on Cartoon Network's Adult Swim strand, in the vein of Aqua Teen Hunger Force or Harvey Birdman, Attorney At Law? Like McCoy's paintings, Quasimoto's music bleeds with a sense of acidic heightened reality, Quas twisting his gritty world into comical shapes for his own jaded, entertainment.

But this is no sleazy, faux gangsta, thrill by proxy, trip; there's ugly sex and uglier violence in Quasimoto's world, because that's the way it is. Batman had his Gotham, Homer Simpson has his beloved Springfield, and Quasimoto has the swarming mess of sin and avarice he lives in.

What they also have in common is that every single one of them is a fictional character.

Deep in Madlib's lair, The New Loopdigga's Hideaway – a studio tucked modestly away somewhere in San Francisco-the day's creativity as begun. Within these cramped walls, the producer-christened Otis Jackson Jr., son of an R'n'b singer and his main songwriter, grandson and nephew to legendary jazz musicians – has recorded hours of music under a plethora of alter egos. The Loopdigga. The Beat Conductor. One-man perv-jazz instrumentalists Yesterdays New Quintet. Jaylib (with producer Jay Dilla). Madvillain (with fellow rap psychedelicist MF Doom).

Today, however, is a Quasimoto session. Perhaps you can tell, by the clouds of weed gathering near the gloomy ceiling, or the scattered records – from treasured rarities to mysterious thrift store acquisitions – piled next totheturntables, where 'Lib is slamming the needle deep into the vinyl with slapdash inspiration, chipping nonsensical slivers of soul, jazz and comedy away to flavour his own concoctions. The giveaway, however, comes when 'Lib steps up to the mic, to give voice to his most beloved creation, stink-fingered ghetto tearaway Quasimoto His beats slowed down to quarter speed, the producer/MC delivers the lines like his lips were dragging through molasses. This is how Quasimoto gets his trademark pitch, a couple of notes higher than Eminem, like he's still giddy after huffing on a cocktail of helium and laughing gas.

There are so many Madlibs out there: the Madlib who produces records for Lootpack, the Madlib who records as Yesterdays New Quintet, the Madlib who pretends he's Quasimoto… Which is the real Madlib?

"I'm Madlib the Loopdigga, I'm Madlib the Beat Conductor, I'm Madlib the asshole, if you want," he slurs with a chuckle, chowing down on chicken in a London Nando's. "I wanna be Madlib the Sleepin' Guy right now, huh huh huh."

Otis Jackson Jr is a tired man right now, though I know from experience that he's not the world's greatest interview subject at the best of times. Otis spends almost every waking hour thinking up beats and tracks, toying with his turntable and writing lyrics. He estimates we've heard barely 1 0 per cent of the music he's made, and he's similarly reluctant to offer much of himself up in interview. Not that he holds anything back deliberately – facts are surrendered willingly, and he demystifies what he can of his various working practices. He even swears weed isn't as crucial to the Quasimoto sound as the album's constant hosannas to the herb would suggest: "I can make music with or without weed," he says. "Back in the days it used to help, but now I'm used to weed; it doesn't really faze me now. My mind's so open already it doesn't even matter."

And the constant references to weed and its creativity-enhancing powers on the records?

"It's just comedy. For people who are barely smoking, and the people who know what we're talking about."

Comedy is a key character of Quasimoto music. Not only are Quas's various adventures mostly ludicrous and hilarious – albeit of a very Furry Freak Brothers/National Lampoon Radio Hour wit – many of the wild, vagrant voices heard on the album are excerpted from old Laff Records, comedians like Redd Foxx and Moms Mabley.

"It's about having fun," says 'Lib. "A lot of people are too serious right now, things are getting crazy. I'm just trying to keep the fun coming, throw up a little comedy.

"I'm, like, basically toned down," he continues, sounding for a moment like the thirty-something family man he actually is. "My shit's not all out there like Quasimoto's. I'm chillin', he's crazy. If I'm in a room full of people, I'll probably just sit there and say nothing. Quas ain't like that."

Though he treads a solitary path, Quas has some homies who ride with him. There's MF Doom, 'Lib's partner in Madvillain. "Doomsday was my favourite album for a long while, " remembers 'Lib. "I called him up, sent him some stuff. He wanted to rap over Yesterday's New Quintet, but I told him I had another idea. He's a cool cat. He's complex, he's not simple. Our lifestyles are kinda the same, except for the stuff that doesn't matter. We don't even have to talk, we could work together all day and not say a word, and it will be cool."

Quasimoto has another partner in crime a croaky voice from the dawn of Blaxploitation, yelling his wisdoms and madness into the uncaring din like Quasimoto's own Mudbone. Melvin Van Peebles is the godfather of rap, after his soundtrack for his pioneering Sweet Sweetback's Baadassss Song. Infamously, he recorded his teenaged son Mario losing his virginity to a prostitute and set it to music. Madlib is now working on Van Peebles' next album. "He's crazy, man," laughs 'Lib. "The first time I met him he grabbed me and told me, 'I'm gonna kill you, motherfucker!' He's legendary, I like him.

For his insane sonic creativity, for the myth he weaves into his tangled records, and for his increasing cult status among clued-in hip hop fans, Madlib is the genre's own Lee Perry. It's another alter-ego, perhaps, a comparison that he likes. "I'm inspired by Lee Perry, read books on him, watched documentaries. I'm kinda productive like him. I don't have a copy of everything I've recorded, but J Rocc of the World Famous Beat Junkies has a complete collection, so I'm always hitting him up to hear stuff, and he says I'm on some Lee Perry shit. If Madlib seems most comfortable playing out his alter egos, but Quas is still the dominant persona.

"He's mischievous, he's badly behaved," ponders 'Lib. '.'He's the reason I don't have to act shit out, huh huh huh."

Quasimoto is an archetype in the line of Stagger Lee, a figure of violent, attractive mischief. Is it more fun to be Quasimoto than Madlib?

"My girlfriend don't like it," he snorts. "She thinks he's real. That's why this is our last album together. He stole my girl."

related artists Madlib, Quasimoto