When Judith Owen and her sister were kids in the London suburbs, they danced around and sang along to the jumping swing-blues of Julia Lee & Her Boyfriends’ “The Spinach Song,” a 1949 single in their dad’s jazz collection.

I didn’t like it the first time
I had it on a date
Although the first time was the worst time
Right now I think it’s great.

“I didn’t know what ‘The Spinach Song’ meant,”...