Ethan Hawke found shooting Blue Moon "frustrating and difficult" - but "rewarding".

The 54-year-old actor has worked with director Richard Linklater for the ninth time on the movie, in which he plays legendary songwriter Lorenz Hart, and the filmmaker kept pushing the star to "disappear" into his character.

Ethan told Variety: "What Rick really wanted me to do was disappear. After a take, my way of critique, Rick would say, 'I saw you.' And any time he saw 'me' he kicked away what I was doing. It was frustrating and difficult. And rewarding. Almost like asking me, 'Can you build this cabinet with those five tools?'"

The Boyhood star drew inspiration on his early days in the New York theatre scene for the role because he could see similarities between his character and his mentors from back then.

He said: "I got my education in the theatre from older gay men. These were intelligent men like Larry (Hart). He's a writer and he's a lover of life and he's got demons and he's in society at a time when being gay was more of an issue.

"I knew people like Larry Hart, with that extreme depth of feeling and perception and insight. They knew everything about theatre, in much the same way monks treat the bible.

"And if you have a mentor who's gay, you're aware, at least back then, that they've spent a large part of life in the closet. I recognized them in Larry and it's heartbreaking."

Although the role was outside of Ethan's "comfort zone", he could still recognise himself in Hart.

He added: "But I also have this person inside me. And Rick knew that. And I knew I was thrilled for this time at bat. This is a role that is outside my comfort zone, but I know this guy. I've played a lot of different characters, but in some ways Larry is the closest to my heart."

The project had been in the pipeline for some time but Richard wanted to make sure his lead actor was "ready" for the role.

Ethan said: "Rick sent me the script 10 years ago. He said back then, 'We're not ready,' meaning I'm not ready."