From Paul Weller to Janelle Monae, striking images show musicians before and after a gig

What do you get if you photograph Elbow, Janelle Monáe, The Prodigy and other performers the moment before a big gig and the moment after? The rock'n'roll effect…

The Gig might be a huge festival or a backstreet dive, yet certain emotions are universal for bands backstage: nervous tension before their entrance; and then, all things being well, euphoric relief as they leave the stage, applause ringing in their ears. As for fans, to witness these scenes up close they'd need an access-all-areas pass (or be the bassist's best mate).

So when photographer Tom Oldham and curator Ed Bartlett got together more than five years ago, it was to create a backstage peephole, to see the lead singer's focused gaze before the roar of welcome on-stage, then the sweat-drenched brow and air-punching a couple of hours later.

In theory, then, the project was simple: travel to club gigs and festivals alike, photograph the artists the moment before they went on stage, then capture them again the moment they got off. Simple, however, doesn't take into account the musicians' labels, which pay handsomely to control how their artists are portrayed – and Bartlett admits that getting permission to shoot so close to performance time was not easy.

Simple, also, doesn't take into account the inevitable unpredictability of the artists – but fortunately, that volatility fed into the project. "The idea was to deliver that unique moment nobody really gets to see," says Bartlett, 38.

Inspired by Annie Leibovitz's 1970s photos of the Rolling Stones, Oldham has produced a collection of stripped-back images of some of the biggest names in rock and pop, from Paul Weller to Janelle Monáe. He had only seconds to grab his portraits in the bustle behind the stage, and that urgency infuses the results. "I never directed," says 44-year-old Oldham. "[The photos] were just an honest reflection of that moment. Gut-honest feelings are displayed."

"Tension and release" is how both Oldham and Bartlett label the difference between the shots. "We always say no towel. We want sweat, we want emotion, we want the relief."

On/Off is the result – a series of portraits compiled into a 72-page book, its production funded by the website Pledge Music, which, through sales, will raise money for the charity War Child.

The book documents 37 performers – though some artists never made the final cut, being "so self-conscious that it took away any form of honesty", says Oldham. So what does it take for the images to work? "It's quite subtle. It's hard to put your finger on it, exactly." But work they do…

For more information about 'On/Off', including ordering details and signed limited-edition prints: pledgemusic.com/projects/warchild