Keane also worked with Charli on Speed Drive for the Barbie soundtrack, but Wuthering Heights came with a very different brief.
They used orchestral elements – recorded at Abbey Road Studios – to help with the gothic feel.
But Keane says he even picked up an instrument himself because they wanted it to “feel really rough”.
“There’s a lot of me playing a really cheap, small violin,” he says.
“And I can’t really play the violin. So it was me just doing these horrible, scratchy sounds.
“When you listen to it, if you hear some really bad raspy playing, that’s going to be me rather than the amazing professionals we brought in.”
Speaking to the BBC at the film’s UK premiere, Charli said she was inspired by artists like The Cure and Kate Bush – whose debut single Wuthering Heights was a number one hit in the 1970s.
Keane agrees, and says they also were inspired by 83-year-old Welsh musician John Cale, who features on House – the first single released from the soundtrack.
“When John Cale sends you this amazing spoken-word poem over music you’ve made, that’s just unreal,” he says, describing it as a “pinch me” moment.