'By the Seventies we were living in the future,” begins Synth Britannia, a documentary that charts the rise of synth pop from suburban England to the world’s dance floors.

Most people’s first exposure to synthesized music was in 1971, on the soundtrack to Stanley Kubrick’s A Clockwork Orange. The film’s sinister score – written and performed on the Moog synthesizer by American composer Walter (now Wendy) Carlos — would lead many listeners always to associate synth with the idea of a bleak and alienating future. Then in 1975, a group of young German men called Kraftwerk appeared on Tomorrow’s World playing only electronic instruments. In the robotic irony and minimalism of the German, short-haired “engineer musicians”, small, isolated pockets of aspiring musicians across the country heard the future.

But what did the British do with this new sound? We did what we’ve always done when we hear a new sound — we distilled it into popular songs.

“We thought we were avant-garde,” says Andy McCluskey of OMD, “but we were the future of pop.”

The synth was all new and you could make a completely original sound on it without any lessons. The only problem was money: in the mid Seventies, a synthesizer could cost as much as a small house. McCluskey bought one from his mother’s Kays catalogue in 36 instalments of £7.76. Joy Division’s Bernard Sumner ordered a self-assembly machine from an electronics magazine and spent two months soldering it together, only to find that “it didn’t work incredibly well”.

But this didn’t matter. These guys were boldly twiddling knobs and pressing buttons no musicians had touched before. British synth poppers were the eccentric, back garden rocket engineers to Kraftwerk’s Nasa. Gary Numan was the first to hit the mainstream when Are 'Friends’ Electric? went to No 1 in 1979. “I’d only had five days’ studio time with a synthesizer,” he says. “There was no time to read manuals. It was a case of 'press that, turn this, that sounds good’.”

Rock critics argued that this wasn’t “real” music. As McCluskey says, they felt “it wasn’t honest, it wasn’t working class, it wasn’t earthy, sweaty, manly.”

It was manufactured. But when had music ever not been? “What’s a piano?” asks John Foxx of Ultravox. “It’s wood that has been felled and carved; lacquer; bits of elephant sawn off and polished and stuff that’s been mined and cast into steel which we stretch into strings which are hit by hammers we activate by pressing keys mechanically. Music is a map of all the mad technologies we’ve co-opted to make nice or exciting noises.”

Today, electronic sounds dominate the charts. But we’ve domesticated the electricity that once sounded so exciting and packed it into little white computers. As Human League founder Martyn Ware says, the element of risk has gone and watching even the pioneering Kraftwerk on their last tour “was like watching four old guys checking their email”.

Three decades on, artists such as Little Boots and La Roux are fetishising the early Brit synth sounds. But that’s just pop eating itself. They’re not yet taking us into new territory. As McCluskey says: “People ask why I don’t like La Roux and I say it just sounds like a woman warbling, badly, over an old Depeche Mode record. We had such a vast, new space to ride into. We were part of the last big wave of Britain inventing something original that rolled out across the world.”

They were the future.

• 'Synth Britannia’ is on BBC Four this Friday at 9pm