As a musician I can definitely tell when a song has been arranged by AI but performed by humans. There are a couple of chart-toppers done this way. I won't give up the ghost, though ;)
are there tells beyond the lyrics? I swear there are a number of songs using out of “human distribution” words, trigrams, etc.
Is it overall song structure?
Nah name-and-shame them!
toupée fallacy
It would be far more interesting if you did. Not sure why you feel need to keep it secret.