Glasgow International art festival: Thirteen hours of performance that explores everything from witchcraft to fashion

Or you can watch Alfred Hitchcock's Psycho slowed down so that it lasts 24 hours, thanks to Douglas Gordon.

Neither, though, is quite as unusual as what I saw at Tramway on Sunday, just upstairs from these much talked-about exhibitions. At dance studio The Work Room, artist Linder Sterling was putting the final touches to The Darktown Cakewalk, an epic, 13-hour performance which will take over the whole of the Arches in Glasgow tomorrow from 11am until midnight. The show has a cast of almost 100 musicians and dancers (doing tango, northern soul, burlesque and more), costumes by fashion designer Richard Nicoll, and explores everything from pop music and fashion to witchcraft and the history of slavery.

Except that "final touches" is not quite right, because The Darktown Cakewalk will be completely improvised. The musicians will meet for the first time today, and preparations at The Work Room have involved just seven core performers, including Linder herself. Nobody involved has any idea how the actual show will turn out – particularly given that audience members can wander in and out as they like, get in the way of the performers, or even join in.

"They can sit under a drumkit, put their head in the bass drum, or lean on a trumpet player," says Linder, who made her name on Manchester's punk scene in the late 1970s. "We have no idea how they'll position themselves. It'll be quite bewildering for people walking in at various points, and quite bewildering for the dancers."

To an outsider, The Work Room preparations can be a little bewildering too. Scattered around the studio are stags' antlers, plastic masks, an electric guitar, and a scary metal object which, as dancer Rachel Smith explains matter-of-factly, will double as a gun and a dildo. The day I visit, the cast does a three-hour improvisation during which they clamber on each other, fight, roll around on the floor, smear cake on their faces, sing at the top of their voices, laugh hysterically, scream, tear at their clothes, and skip like children. Later, one of the performers covers her face and arms with white paint and recites Jade Goody's apology to Shilpa Shetty on Celebrity Big Brother, while Linder lies on top of her, practically choking the words out of her. This, Linder later decides, might be a good way to end the show.

The performer in question is Laura Cameron-Lewis, creative co-ordinator of The Work Room. Normally her job is a little more office-based than this; since the artist-led studio began offering residencies to dancers and choreographers in January last year, her role, she explains, has been "to support the development of innovative new works, with an emphasis on process".

Much of the time, this means making practical decisions about who gets to use the space and when (Natasha Gilmore, Anna Krzystek or Diane Torr are among the artists given residencies so far) but Cameron, a professional performer herself, is happy to be more hands-on when she's asked to. "I facilitate the work of very different artists, each with unique vision and method," she says. "Every situation requires an improvised response. That is exactly what has happened in The Work Room studio during Linder's residency. In many ways, her artistic vision parallels the artistic policy I aim to deliver for The Work Room."

She praises Linder's "phenomenal sense of composition", creating a collage out of the performers' individual efforts: "It's a bit like working with found objects, except that the objects are human, they talk back, they have needs. This is why the durational element (the length] of the performance is so necessary, to articulate these epic shifts in relationships and meaning."

Through six core archetypal characters – the Star, the Muse, the Witch, the Cakewalk King and Queen and the Puella Eterna (the eternal girl), The Darktown Cakewalk sets out to explore the links between the cakewalk – originally invented by black slaves on plantations as a way of mocking their owners, but later co-opted by white people – and modern beauty pageants, and between witchcraft, fashion and celebrity (the word glamour, Linder points out, has its origins in witchcraft). "Witches were executed for their glamour, beauty queens are judged for their glamour, slaves are judged," she explains. "We're looking for the subtleties and nuances in all these archetypes." The show's 13-hour length is inspired by music hall, which would normally feature 13 acts per show.

In the three-hour improv I saw, the dominant character is the Star (Tom Pritchard), who starts out as a nave pop wannabe and ends up as a debauched, spoiled brat yelling "why aren't you cheering?" and is then mocked by the other characters, who pull his trousers down and laugh hysterically at him.

"That was a total accident," says Rachel Smith (the Catwalk King) afterwards. "Over big stretches of time we have a notion of what part of our character we're embodying so the interactions between us have a similar kind of energy about them, but what we do each time, physically, is completely different. You could never engineer it to happen again."

The point of The Work Room residency, Linder explains, has been for the core performers "to build up an intuitive sense of each other" so that, once they're thrown into the vast space at the Arches, and surrounded by other dancers, musicians and unpredictable audience members, they will still know "how to lock into each other". I suspect that won't be a problem. Watching the seven performers role-playing together, you can't help but be impressed at their chemistry, not to mention their gleeful lack of inhibition.

After Pritchard has his trousers pulled down, Linder and Judith Williams end up rolling around on the floor making orgasmic yelps, while Pritchard breathes heavily into a microphone at the other end of the room.

Shortly afterwards Williams is to be found standing on a chair, dressed in nothing but a black bodystocking, singing Smile by Judy Garland so ear-piercingly loudly that I worry the studio mirror will break.

What does it all mean? Come along tomorrow and find out.

The Darktown Cakewalk: Celebrated From The House of FAME is at the Arches, Glasgow, tomorrow, from 11am, as part of the Glasgow International art festival. www.glasgowinternational.org. Linder Sterling is also showing work at the gallery of Sorcha Dallas, who is producing The Darktown Cakewalk, until 22 May. www.sorchadallas.com