Grand Canal Theatre, Dublin Until Jan 7 7.30pm (mat 2.30pm) €20-€55 grandcanal theatre.ie 01-6777999

Is nothing sacred? Musical theatre certainly thinks not. Here's a genre that has always cannibalised other stories and forms for material – the literary sources of West Side Storyor Phantom of the Opera, the hijacked opera of Miss Saigon, the poetry transplanted into the furballs of Cats. It's an entertainment so joyfully commercial that it's hard not to be dazzled by it. But the musical may have found its most fertile sources in two other media: the back-catalogues of mega-selling music groups and, of course, the movies.

Mel Brooks's film The Producerswas halfway there already, as was John Waters's Hairspray, and the later film versions of the stage versions of the original film versions suggested a business model based on the logic of a vortex.

For the moment, Sister Actseems more simple: big, brassy Motown music in a wimple. Its plot also mirrors its adaptation with a beneficial trade: the sassy sinner Deloris Van Cartier, in hiding from the mob, learns sympathy from an order of nuns while their dowdy choir gets the chance to become a belting chorus line.

Such are the DVD-sized pleasures of a good night in. But the musical empire has learned how to transform that into a big night out.

Can't see that? Catch this: Shortcut to HallelujahTown Hall Theatre, Galway