Acclaimed Flop: Downplayed a bit, while it made its small budget back, it's also the lowest-grossing movie ever to be nominated for Best Picture. What doesn't help was the film never left it's limited release.
Cast the Expert: Naturally, several of the musician roles went to actors with advanced musical backgrounds or actual musicians. For example, Carlnote (the initial core drummer in Fletcher's band) is played by Nate Lang, who is also a professional drummer who trained Miles Teller and Austin Stowell into their roles.
During the jazz bar scene, that really is J.K. Simmons playing piano — while he did have to take refresher lessons, he used to play frequently and comes from a family of musicians.
To a lesser extent, Miles Teller was a drummer since his mid-teens and took additional lessons, though a double was used for certain parts and shots.
Critical Research Failure: Andrew's expulsion letter reveals that the film takes place in 2014. However, he later participates in the JVC Jazz Festival, which was renamed the Newport Jazz Festival in 2009.
Determinator: Director Damien Chazelle was in a car accident during the third week of a 19-day shoot and hospitalized with a possible concussion, and promptly returned to the set the next day.
Doing It for the Art: Everyone attached to the film. The film had a 19-day shoot with a grueling 14 hour-a-day schedule, but everyone pulled through to make the movie happen.
In one scene Fletcher repeatedly slaps Andrew while making him do a four count and trying to get him to figure out if Andrew's tempo was too slow or too fast. The actors, after doing a few takes where Simmons only mock slapped Teller, decided to do one take where Simmons slapped him for real. That was the take they used.
During the scenes where Andrew and the other drummers are exhausted, takes would often run into each other to actually make them tired. This even extended to Miles Teller ending up with real blisters and bleeding sores from overplaying, making some of the blood actually his.
Non-Singing Voice: An instrumental variation: Miles Teller is seen playing in most of the shots, and so there is no clear Talent Double (whether or not the closeup hand shots were Teller's, they focus more on Andrew's bleeding fingers than his skill), but the drumming that we hear was recorded by studio musicians. Teller is often out of sync with the recorded track, but skillful editing makes it non-obvious.
Write What You Know: Damien Chazelle wrote and directed this movie based on his own experiences in jazz drumming. Moreover, in a piece written for the Los Angeles Times, Chazelle reveals that his experiences influenced his film's thematic questions of how far one should go for greatness and what greatness even means. Jazz musicians have noted that Damien Chazelle's experience of jazz drumming are limited to his experience of drumming in a high school big band, and that the film contains too many examples of Artistic License Music for this trope to be entirely appropriate.