I just read Joni Mitchell's biography, and it sounds like the whole music industry was coked up for 10 years in the 70s. She tells a story about The Last Waltz and how Robbie and Neil were so high that they were way off key, and Neil had a cocaine booger dripping down his face that the director tried to airbrush out of the film.
https://www.cbcmusic.ca/posts/17644/...ine-neil-young