In this video of Nirvana's 1992 Live at Reading performance, Kurt screams out the song "Tourette's" (35:10), and it sounds like he's absolutely destroying his vocal chords. Then, at 37:04, he's singing the much quieter song "Polly" with almost perfect pitch. I've heard vocal coaches say that a lot of grunge singers don't really do anything properly or even healthily, and it sure sounds that way in "Tourette's". But he transitions so nicely into "Polly" that I have a hard time believing he wasn't using some kind of screaming technique. Did Kurt actually use proper technique when screaming like he did in "Tourette's" in order to be able to continue the concert? Or did he just have invincible vocal chords?