... a "My Song.wav" in the same directory, with the same name, but I always considered that a bug - not a feature, since it will confuse the heck out of new users at some point.
It certainly confused the Hell out of me, as that .wav file will/can then be read back into BiaB and plays alongside the normal tracks, causing some very puzzling behaviours.
And if we new users don't know that's what happens, may not either be aware of that, so we may well not mention when reporting those strange behaviours.
Henry Clarke highlights this and some "good practices" to circumvent the problem in one of his (excellent, IMHO) BiaB tutorials. Ah ... here it is, there's an explanation of how he uses utility tracks and how to manage the .wav files.:
https://youtu.be/XiPqQjISmb4?list=PLNGYsTA3YLQSZv0fgfcy0ukVF7zW2JSJu&t=320