After listening to Willie McTell for over 50 years, I just found out that one of my favourites of his, (which I assumed he's written,Baby It Must Be Love.) was originally done by Bob Howard. You can hear it on You Tube. McTell changed the melody, but all the lyrics are the same. You can also see Bob Howard singing, "Shine". After watching hime you can see that he was obviously a big Fats Waller fan & modelled himself on Fats.
You live & learn.