I hate this view, it’s not true, at all. The majority of great musicians are normal people. This is a concept people made up to justify liking shitty people. I’ve personally interacted with a ton of my favorite bands and outside of a few assholes they are all cool normal people. Music is a rational thing, there are formulas for what does and does not work, you don’t need to be insane to do cool and innovative shit with music. If you look at most of the people that were insane they burned out, died, or ended up in obscurity. Insanity is a universally detrimental thing to experience, it doesn’t impart any kind of gifts. They’re also usually credit stealing narcissists, like Jim Morrisson, they don’t actually provide anything to the music other than a face and personality.

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EDIT : To be clear, I am not saying "his musical output is caused by/limited by/due to" his insanity. I mean his mental illness makes his productivity less efficient to the point where there is less output.

So if he's being affected by mental health, it doesn't matter if it's his music or his kid's music, neither is getting completed because he's not going to get anything done, because mental health problems will impede his productivity.