John Lennon was raised by his Aunt Mimi, who is usually described with words like “strict but loving.” And while there is some debate among Beatle people over exactly how “loving” she really was, nobody questions the “strict” part. As you can imagine, then, she was not a big fan of young John’s obsession with rock and roll, or his non-stop guitar practice.

“The guitar’s all well and good, John,” she would say, “but you’ll never make a living at it.”

Years ...