Originally Posted by Bass Thumper
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Levitin doesn’t spend a lot of time on music “education” per-se but he does say:

Many of the greatest musicians of our era lacked formal training, including Sinatra, Louis Armstrong, John Coltrane, Eric Clapton, Eddie Van Halen, Stevie Wonder and Joni Mitchell. And in classical music, George Gershwin, Mussorgsky and David Helfgott are among those who lacked formal training, and Beethoven considered his own training to have been poor according to his diaries.

IMHO if you take all of the musicians in an orchestra, pit bands, bands backing TV shows, etc I would bet that those who made it with no formal training is a small minority. Plus of those whom you listed I'll bet some can read music so they did have some formal training.

https://www.louisarmstronghouse.org/faq/could-louis-armstrong-read-music/
https://faroutmagazine.co.uk/song-joni-mitchell-relearn-piano-david-crosby/

I guess the real question is what does one consider as formal training. Lessons on a instrument? A college degree?

When I was teaching theory to my guitar and bass students I stressed learn theory but don't let it dictate your playing. Learn theory to enhance your skill bass (scales, how chords are formed,etc) and to analyze what you played but always play from your heart. YMMV

The bumper sticker said "I'm a veterinarian, therefore I can drive like an animal".
Suddenly I realized how many proctologists are on the road.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware