In the category of Strange Things I Didn't Know 10 Minutes Ago:

Apparently, there's something special about the note of B flat. Play it to a male alligator and he'll bellow back at you. No one knows why, he just does it. Only for B flat. And, just to increase the strange factor, there's a black hole out there that is more or less humming to a nearby gas cloud, humming in the frequency of B flat.

Sort of makes one want to go around with a B flat and see what else out there sings back...