Musicians making movies is a risky business - but Outkast have always been an act where worlds collide. Atlanta-raised duo André 3000 and Big Boi spliced hip hop, soul and electronica into a vivid musical hybrid, internationally established through hits including Ms Jackson (2000) and crystallised on 2003's 11-times-platinum double-album Speakerboxxx/The Love Below. Now their latest project, Idlewild, experiments with new songs and another dimension: the big screen.

Idlewild is a musical adventure set in the Prohibition-era Deep South, scripted and directed by long-time collaborator Bryan Barber, who created several Outkast music videos. On screen, AndrÈ is a natural showman (famously playing several leads for the Hey Ya! video). Talking to me, he's a sleepy-sounding Southern gentleman: "Well, I'm feeling just fine; how are you?"

Since commencing Idlewild two years ago, he's also racked up roles in movies including Four Brothers, Be Cool and Revolver.

"Actually, Idlewild's songs came before the movie," explains André. "The film is an extension of our videos, because we've been writing all kinds of scripts with Bryan for years. I guess it finally got to the stage where movie studios were willing to invest in our ideas.

"My film character is called Percival. He's a mortician's son who plays jazz piano by night in Church, a juke joint owned by Rooster - that's Big Boi. Sure, the story is set in the past, but the music connects more with modern audiences."

In fact, Outkast's film and imminent 25-track album (also called Idlewild) are complementary yet quite independent of each other.

The same could be said of the duo, credited on screen under their real names André Benjamin and Antwan A Patton. They play childhood friends "from two totally different sides of the track with the one common ground - music".

As real-life former classmates, whose music spans 15 years, they've rebuffed rumours of internal rifts, although AndrÈ admits: "Everything we do is kind of a reaction to events. After Speakerboxxx and The Love Below, we couldn't do another twopart album, it wouldn't be cool to keep beating the same horse. We don't sit around thinking of new ways to be different and exciting."

He sighs: "But yeah, there's plenty of times you think of giving up. That's why I don't tour, although Big Boi goes out on stage and does his thing."

The dynamic between them remains jealously guarded.

At least Outkast are never serious for too long. Their imagery boasts a boundless, child-like imagination; interestingly, the brightly-hued video for their next single Morris Brown bears no relation to Idlewild's period film visuals. And André sounds most animated when he talks about starring in his own cartoon series scheduled for this autumn, Class Of 3000.

"Cartoon Network approached me after The Love Below was released but I didn't want to adapt the album into a cartoon. So this show is about a superstar called Sunny Bridges who ends up as a music teacher at a school for exceptionally gifted kids. I voice his character and there are new songs in every episode, but it doesn't sound like kids music.

"Yeah, I liked the idea of being a prime-time cartoon character, and he does look like me, a bit!"

Judging by Idlewild's preview clips, the film exudes cartoonish energy, too - Outkast spruced up in zoot suits, flanked by seasoned actors and singers (Terrence Howard, Macy Gray, Patti LaBelle and Ving Rhames also star) and formation lindy hoppers.

Its roots run through their previous works (there's even a sneaky mortician theme in the Hey Ya! video) and André is philosophical about its prospects: "We never really fit into the normal playlist but we know we can reach a lot of people. As for the future, it all depends on whether the audience is willing to go with us."

Right now, it's a compelling trip. Outkast still dream up their tunes in glorious Technicolor.

Idlewild, the album (RCA) is released on Monday. Outkast's film is released in October.