"All rock'n'roll should be larger than life." Once more, with feeling, Scissor Sisters are back - bearing their second album, Ta-Dah - and lithe frontman Jake Shears is waxing lyrical: "I want our records to send your imagination into overdrive."

Several storeys below their hotel room lies London's Theatreland and the hubbub of Trafalgar Square, where Scissor Sisters play a sold-out charity show this weekend.

Ta-Dah heralds a fresh blast of pop extravaganza (including their first No.1, the bittersweet stomper I Don't Feel Like Dancin'), propelling the quintet - Jake, classically-trained co-founder Babydaddy, selfprofessed "drag queen stuck in a woman's body" vocal sidekick Ana Matronic, guitarist Del Marquis and drummer Paddy Boom - into another giddy showbiz whirl. But are they psyched for it this time?

"When we got off the last tour, I had a really hard time readjusting to normal life in New York," admits Jake. "I couldn't deal with any creative output - written words, movies or music. I wanted to make good songs so obsessively, it paralysed me. I'd shut people out. I'd walk into a store, a song would come on, and it'd send me into a panic."

Medicine for Jake's soul eventually came in unusual forms. One was the music of US psychedelic veteran Van Dyke Parks, who contributes to new Scissor Sisters track Intermission (featuring the jaunty refrain: "Tomorrow's not what it used to be/ We were born to die").

Another was the Magic Kingdom of his recurring dreams: "Disney World was a huge influence for this record," he explains. "Especially when I rediscovered Song Of The South, a Disney movie about a slave entertaining white children with his funny stories. There's something so dark and demented about it - I find that really inspiring."

Produced in the Scissor Sisters' customised Discoball Jazzfest studios ("Babydaddy twiddles the knobs and I backseat-drive," grins Jake), Ta-Dah sounds both lavishly theatrical and intensely personal. One moving highlight, Might Tell You Tonight, is written for Jake's boyfriend. As with their self-titled 2004 debut, the band's wild contradictions bond against the odds. "Trying to control a band like ours is like trying to corral a bunch of kittens - one's always wandering off," says Paddy.

"And then you wanna put 'em in a bag and drown 'em," adds Del. "We're fiercely individual and sometimes get at each other's throats but it all makes the Scissor Sisters great." Anyone who's witnessed Scissor Sisters' vamped-up live spectacle will know that they're exceptional entertainers - but who do they rate as a showman? "Prince," says Del, firmly. "He makes it look so easy - and he keeps his clothes on."

"Unlike me," quips Jake. "I think Mick Jagger is the best frontman ever," he adds. "He pushes all the right buttons."

Have they ever considered starring in their own West End/Broadway musical? "No, theatre doesn't interest me because of its impermanence. I'm much more into psychedelic film," says Jake. But isn't Scissor Sisters' music about living for the moment?

"Onstage, it's totally about the moment," nods Paddy. "It's almost like jumping off a cliff every night. I think we're lucky to be ambassadors of pure joy."

"It's also about not taking things for granted," says Jake. "There's nothing bitchy or cynical on this album, and I'm proud of that. We're living in a world at war - you might say, what business do we have making pop music right now?" His eyes widen at the possibilities. "I say - the band on the Titanic didn't stop playing."

Scissor Sisters play a charity show in Trafalgar Square on Saturday, highlighting the initiative to eliminate Aids in Africa. See www.motorola.com/red. The show is televised that night on Channel 4 at 10.40pm. Ta-Dah (Polydor) is out on Monday. See that day's Metro for a review.