Audio problem: When they are playing "Whiplash" it shows a hand playing piano. When the hand is going up the piano (to the right) the music goes up, then down. Going up the piano should only play higher notes. (00:18:20)
Audio problem: When Nee-man gets his first blister when practicing the drums alone, he punches and breaks his fist through the snare drum. He continues to rock on with the snare drum audible in the practice exercise soundtrack, immediately after breaking it. (01:00:00)
Chosen answer: No, it is not normal to bleed while playing drums, as callouses develop on a drummer's hands through constant practising and playing. But, if a drummer plays hard enough and fast enough using the same drum sticks, friction between wood and skin can develop and rupture toughened skin. In the context of the film, the drummer is being pushed beyond his limits by the music conductor. Additionally, he is pushing himself to be better, so the bleeding is a consequence of that drive for excellence.
Scott215