From his offensive demeanour to his all-in-black attire, Fletcher is a frightening creation by Simmons - almost as repellent as his feared inmate Vern Schillinger in the HBO series . "[The physicality] seemed to me part of this regimented disciplinarian way of life that he lived himself and tried to impose on his students," says the 59-year-old actor. "And also part of his intimidation tactic - he would be this almost militaristic, erect, fit and imposing kind of character … just to help him assert his will on everyone."

Having played drums in his youth growing up in Rhode Island, with "an inspirational but terrifying teacher", Chazelle based on his own experiences. "The thing that makes drumming special is it's the most basically physical instrument. You're ultimately spending your time just banging things, so there is something brutal and elemental and sometimes angry about it, so it made sense for this kind of movie. It's kind of like boxing." He pauses. "You're always fighting for a level that you never quite attain."

Likewise, Simmons understood Fletcher's aggressive behaviour. "Everything he does is motivated - and perverted - by his love for the music," he says of his character. The Detroit-born actor studied music in college and his old professor was similarly exacting.

"He said that our first task is to get it perfect and then we can make it great. But you have to be technically proficient and flawless before you can begin to make art; so to play a guy who is a relentless, abusive bastard like that, you have to find the motivation for it."

Simmons' own father, Donald William Simmons, was a music professor at the University of Montana - and about as far removed from Fletcher as you could get. "I saw my father as this really charismatic teacher who inspired curiosity and a love of music. It was a beautiful thing to see," the actor says.

A music film that reads more like an underdog sports story - albeit one that undercuts the usual triumphant conclusion - is far more about the dedication it takes than the end result. And it's why Chazelle even invokes the mythical tale of how, as a 16-year-old, jazz great Charlie Parker had a cymbal thrown at his feet in disgust by a fellow musician during a live performance - a humiliation that saw him dedicate the next 12 months to intense practice.

"I intended it to be both an alarm and inspiration," says the director about . "I think the behaviour in the film is monstrous and horrible but I like the idea of talent not being something that you're born with, that it's something you develop from working hard, that anyone can be great ifthey really work at it enough. The 10,000 hours rule - I do believe in that, so that's also there in the movie too. But I wanted also to go all the way in showing how f*****d up that life can be."

Chazelle, who spent four years learning the drums, is clearly fascinated by music. His first film, 2009's , was a love story revolving around a young jazz trumpet player.

While he's not as confrontational as Terence Fletcher, he did have his moments - notably the scene where Simmons' character is putting three drummers through their paces. "We just did the whole scene in one take. Then we did it again. Then we did it again. Then we did it again. Often without cutting. Then I'd yell, 'Go again, go again'. And we did that probably 10, 15 times in a row without stopping. By the end, the sweat is real.

"Suffering for your art … I think that's a very interesting idea," Chazelle says. And that, as any artist knows, is how you get results.