Story of the song: I’m Not in Love by 10cc

Acerbic and witty, 10cc were pop’s smarty-pants, and the mesmerising “I’m Not in Love” their cleverest song. Eric Stewart was inspired to write the lyrics of the 1975 hit after his wife complained that he didn’t tell her that he loved her often enough. He set about figuring out another way of saying it. “I chose to say, ‘I’m not in love with you’, while subtly giving all the reasons throughout the song why I could never let go of this relationship,” he told Sound on Sound magazine.

Stewart prepared a guitar hook that fitted the cadence of the title. “I made things fit phonetically, and it just sort of rolled out very smoothly in a bossa nova shuffle,” he said. “I’m not in love / So don’t forget it / It’s just a silly phase I'm going through.”

He then invited his bandmate Graham Gouldman to help finish it off. Using just guitars, the duo pushed square chords into round holes, and ignored the conventions of chorus and middle-eight, to avoid a “regular” pop song. The initial demo was dismissed as too cute by the other half of 10cc, Kevin Godley and Lol Creme, but eventually they agreed to give it a go.

In Strawberry Studios, a converted armaments factory, with iron pillars clad in thick carpet, the band set about recording their Brazilian number, taking Steely Dan's button-bright sound as their cue. Godley liked it even less. “I’m Not in Love” was binned and the band moved on.

But the song wouldn't die. Stewart kept hearing staff humming the title line and, after a few days, a studio secretary asked him to finish it. Godley suggested that the only way it would work would be with just voices, a cappella. Tape loops were prepared of the four band members singing. A bass solo, Moog and Fender Rhodes piano were added, and, with no metronome, the extensive overdubs and loops were all marshalled into tempo. The secretary put on her best telephone voice for the line, “Be quiet. Big boys don't cry”, and a musical box was dubbed into the fade-out.

Stewart was vindicated. “I was looking at Kevin and the other two guys saying, ‘What have we created? This is brilliant!'.” Reluctantly, their label issued the six-minute ballad as a single and it shot to No 1.