Acting
J.K. Simmons was already terrifying in 2013.
Direction
Every cut is a drumstick to your nerves.
Editing
Proof that editing IS the music.

Director
Damien Chazelle
Trivia, insights & behind the scenes
Chazelle couldn't get funding for the feature, so he made this short as proof-of-concept—using the same actor (J.K. Simmons) and nearly identical scenes.
This short essentially blackmailed Hollywood: 'Fund the feature or this masterpiece stays buried.' It worked.