It's the drill instructor from Full Metal Jacket as a jazz instructor.

Rating: 9/10 (31 May 2018)

Whiplash is a great film for a few reasons, the same reasons for which it won its corresponding awards. J.K. Simmons does an excellent performance, the sound design is excellent, and the editing is excellent. Beyond this, there is nothing particularly excellent in the film, and a number of elements to find fault though the pros largely outweigh the cons.
Probably the most interesting aspect of the film is J.K. Simmons' performance as Terence Fletcher, a ruthless jazz instructor. Every moment that he is on screen is intense and often comical in a very cruel way, almost to a comical degree. His character is basically that of the drill sergeant from Full Metal Jacket, throwing vulgar insults at his students without hesitation. Thankfully, he's a huge part of this film, thus he is allowed to carry it drastically. He's a lot of fun, and his performance is one of the most high energy performances I have seen this decade. Miles Teller did a fine job as Andrew Neiman, but he is largely overshadowed by his antagonizing instructor.
The editing also played a huge role in the entertainment value of this film. The pacing felt just about perfect, which is especially important in a musical film. The beats through the film are almost rhythmic, making the film seem fully realized in its premise, elevating it far above the usual mediocrity, which also aids in Fletcher's attempts at beating perfection out of his students. It's a thoroughly exciting film largely in part to the editing. It truly is thoroughly exciting and quite inspirational in an extremely tough, critical way that has almost become extinct in today's politically correct society.
The sound design is an extremely important aspect in a musical film, and it's certainly excellent in this film. There are no distracting elements throughout the film, as everything is right at the level it needs to be. The soundtrack is as intense as the film itself, and is never overwhelmed by external sources, even with Fletcher throwing in insults during live performances. Aside from one intentionally stylized sequence, the visuals perfectly match the audio in the musical performances throughout, and there are moments in which the film isn't afraid to shake things up and provide us with scenarios in which the main character messes up performances for specific reasons, such as injury, or being made to play a piece he couldn't have known prior, and the results are suitably bad in a believable way.
One gripe I have with this film is just how unbelievable the circumstances are. I cannot suspend my disbelief as in reality someone like Fletcher would most certainly be immediately fired, and likely sued on top of that. Not only is he verbally abusive throughout the film, but he is also physically violent as well. There's a scene where he slaps our main character repeatedly to train him to keep proper tempo, and this simply wouldn't fly in real life, especially not in a large class like Fletcher's. Not only this, but he also demands the drummers to play as fast as they can for literally hours until their hands are bleeding significantly during one practice session. Beyond this, he also kicks and tosses furniture around, sometimes at students, and his excuse for this is that a famous musician, Charlie Parker, didn't become great until he was "nearly decapitated" with a cymbal thrown at him. This is however grossly exaggerated, as the cymbal was thrown at Parker's feet. While I can accept Fletcher's reasoning for tough love and the harm in saying "good job" to a talented individual, as complacency is the death of art and a huge problem especially in this day and age.
Fletcher's critical attitude seems very unrealistic to me. Fletcher's ability to determine tempo with microscopic accuracy almost comes off as a super power. While I could agree with him at times, at others he would flip out for something that by any reasonable standards was close enough to be indiscernible. The movie almost devolved into insanity as it made a simple beat out to be the most impossible task in the entire world.
The plot isn't all too engaging either. It's simple, and is serviceable, but it didn't astonish me. The ending was largely unsatisfying, as the main character felt less triumphant and more so like a battered housewife with Stockholm Syndrome. Fletcher doesn't quite get his comeuppance, and Neiman doesn't quite stand up for himself. It's simply not all that satisfying, and the one moment where Neiman finally breaks down and attacks Fletcher is too light and too short-lived to make it satisfying.
Most other elements were fine but not beyond fine. Supporting characters were sort of just there, and didn't really add more to the film rather than being stand-ins or human punching bags for Fletcher. It's almost odd that as the movie goes on, Fletcher seems to ignore all of his other students and simply focuses on Neiman with all of his attention and criticism by the end.
I would recommend this movie to just about anybody, except grandma perhaps, as she might find the language offensive. It's certainly interesting enough to watch either on a casual level or a critical level.