As modern Hollywood partnerships go, there probably isn’t a more enduring one than Ethan Hawke and Richard Linklater. Hawke first worked on the director’s 1995 film Before Sunrise and they’ve not stopped since. ‘We just keep talking and these movies come out of that,’ he explains when we meet at the Berlin Film Festival. Their latest venture is the ninth of this long-standing friendship: Blue Moon, a film that, curiously enough, is all about creative partnerships.

Hawke plays Lorenz Hart, the Broadway lyricist who co-wrote such indelible songs as ‘My Funny Valentine’ and ‘Blue Moon’ with Richard Rodgers. But blighted by alcohol addiction, his time came to an end with Rodgers, who found a new partner: Oscar Hammerstein. Over time, Rodgers and Hammerstein became the most successful duo in musical history, creating shows such as South Pacific and The Sound Of Music, overshadowing any achievements with Hart. Linklater’s Blue Moon is set entirely at the after-show bash for the first Rodgers and Hammerstein production, 1943’s Oklahoma!, as Hart enviously looks on and realises his time is up.

‘Growing up in the theatre community, I find that whole period very romantic, imagining those opening night parties and those relationships,’ says Hawke, who appears on screen with a (slightly disconcerting) combover and looking shorter than everyone else, replicating Hart’s 5ft 5in stature. ‘When I think about people who played Johnny Cash or Muhammad Ali… we know what they look like, and we’ve heard them talk. Nobody knows Larry Hart. So it’s a huge relief, because I can read books about him, read his letters and learn about him. But I can just take what interests me, as opposed to feeling obligated to go, “why didn’t you capture this side of him that’s so important?”, because people don’t know much about him.’

Playing Rodgers is Andrew Scott, who won Best Supporting Performance in Berlin this year for that role. Hawke compares their on-screen dynamic to a break-up. ‘It’s almost like meeting a couple who were married for 20 years, but you’re watching them the day after they got divorced. It was challenging for Andrew and I to sense the history. Larry Hart was the mentor, then became the peer, then he was the student of, and then he was dismissed.’

Fortunately Hawke, who turns 55 this month, is far from being dismissed, with new roles this autumn in horror film Black Phone 2 and TV detective drama The Lowdown. But, as a symbol of the 1990s American independent scene, he feels the filmmaking he was fascinated by when he was young is out of fashion now. ‘I never dreamed of car chases or zombie movies. My dream was, “what would it be like to be Max von Sydow?” It’s tough: those movies aren’t happening.’

Calling himself ‘genre agnostic’, Hawke is keen to try as many different types of films before he retires, including a broad comedy. ‘I’d love it if Will Ferrell asked me to play his brother.’ If nothing else, the four-time Oscar nominee will always have Linklater, though he’s amazed the director keeps hiring him. ‘He’s spent years of his life editing my performances,’ Hawke remarks. ‘I mean, he must be bored shitless!’

Blue Moon is in cinemas from Friday 28 November.