Kurt Cobain didn’t seem to have any sense of self-preservation when singing with Nirvana. As far as he was concerned, whatever came out was going to be authentic to how he was feeling in the moment, and if that meant singing in a whisper or shrieking his guts out, he was going to make sure that he gave his everything once he had a microphone in front of him. If you’re pushing that hard, it’s not hard to see why some problems come up, and ‘Lithiu…