He never learned the first thing about music

[Undertoad]

"I didn't and still don't know... an F# from a chocolate donut."

So said the great Bill Withers, who wrote "Ain't No Sunshine", "Lean on Me", "Lovely Day" and "Just the Two of Us".

Wikipedia says

Withers worked assembling toilets for Boeing 747's, while recording demo tapes he shopped around and performing in the juke joints during the night. When he debuted on the music scene with "Ain't No Sunshine" he refused to give up his job because of his belief that the music business was a fickle industry and that he was still a novice compared to other working acts like The Temptations or Sammy Davis, Jr.

And he was right - but if you have two mega-hits, you're rich, and with 5-6 under his belt he's surely as well-off as he deserves to be, for writing such lean but memorable songs.

The guy never learned the most basic music theory. He simply wrote songs. Great ones.

You have to wonder why anybody learns theory, if "Lean on Me" doesn't require it.