If the song doesn't work, just change the singer

Sloppy seconds? ... Madonna's Hard Candy album

So not only has Madonna's Hard Candy album been a fan dividing exercise in re-tooling Madge as some sort of R'n'B queen, it's also revealed some nasty truths about some of her collaborators.

No, not the ongoing debate over whether Timbaland nicked the swizzly bits on 4 Minutes to Save the World from Crystal Castles, but the fact that the Neptunes may have not been completely honest with her.

The controversial track in question is Heartbeat, which was originally written for Pussycat Dolls singer Nicole Scherzinger's now-shelved solo album. However, the demo has now found its was onto the internet.

Given the limited number of in-demand songwriters around, it's only natural that recycling tracks for different artists should take place. Cathy Dennis famously wrote Sweet Dreams My LA Ex for Britney Spears as a dignified response to Justin Timberlake's Cry Me A River. In a bad, bad career move, Brits passed on it, moving Dennis to give it to Rachel Stevens.

Meanwhile, Max Martin originally offered Baby One More Time to TLC before giving it to Britney Spears. Martin also offered Since You Been Gone to Pink before Kelly Clarkson got her hands on it.

These are well known, but a little digging finds some more interesting examples.

Take Don't Cha, which Gnarls Barkley's Cee-Lo wrote with a little help from Sir Mix A Lot. The Pussycat Dolls made it a hit, but Tori Alamaze, the former backing vocalist for OutKast, recorded this version in 2004. And it doesn't have Busta Rhymes perving over the top either. Bonus!

Bev 'Coulda Woulda Shoulda' Knight released a typically soulful single in the shape of Keep This Fire Burning in 2005 with a charmingly silly video. Who knew a post-first flush of fame Robyn had previously recorded a version for her third album in 2002?

Finally, most people would put Beyoncé on another musical planet to Victoria Beckham. Funny, then, that in 2006 B would re-record a song, Resentment, from Beckham's shelved 2004 second album.

So which other re-recorded demos or secret cover versions have gone on to be huge hits?