The director and writer of the film, Damien Chazelle, could not get funding for the movie, so he instead turned it into a short film and submitted it into the Sundance Film Festival in 2013. The short film ended up winning the Short Film Jury Award, and he got funding soon after.
The film was shot in 20 days. And nearly a full day was dedicated to a scene in Fletcher's office that was cut from the final movie. Still, Damian Chazelle believes the scene ultimately helped Miles Teller and J.K. Simmons develop their chemistry.
For the slapping scene, J.K. Simmons and Miles Teller filmed several takes with Simmons only miming the slap. For the final take, Simmons and Teller decided to film the scene with a real, genuine slap. This is the take that is in the film.
During the more intense practice scenes, the director wouldn't yell, "cut!" so that Miles Teller would keep drumming until he exhausted himself.