I just found out about this, and I find it fascinating. In 1959, Bobby Worth turned Puccini's "Quando m'en vo," a.k.a. "Musetta's Waltz," from La Boheme, into a pop song titled "Don't You Know?," which was recorded and turned into a hit by Della Reese.
Here is the Puccini original (a live recording with Maria Callas):
Here is Della Reese's original recording of 1959:
Here is a live recording of it that she did with the Duke Ellington Orchestra in 1962:
And here is another live recording (a later one, I would judge by her voice and the arrangement):
Just listen to how, slowly, over the years, the traces of Puccini's original orchestration (and instrumental counterpoint lines) fall away, and how Della Reese's vocal delivery turns more and more into the blues. A blues written by Puccini.
Honestly, I probably still prefer the original version (I was looking for the Toscanini version, with Anne McKnight singing Musetta, but couldn't find it online), but it's great to see the song survive as more than a museum piece. (I just wish Bobby Worth had kept the import of the original italian lyrics, they are a lot more interesting than the English text.)
I have to dedicate this post to another Anne McKnight I know, to whom I remember writing in a letter (those were the days!) about the Toscanini recording, well over two decades ago.