It’s crazy how many videos I’ve seen of dogs reacting specifically to this song. I’d guess it’s the pitch the harmonica is at but that’s a pure guess. My own dogs will also howl at this one, but they really like “Golden Years” and “Fame” by David Bowie
My hound/pit mix loves the “wopwopwop” background singing Bowie does on Golden Years and it makes him do the adorable cocked head things dogs do when they really want to focus on something It’s like they have to hone their radar dishes in on it to figure it out
My dog Tiny was a huge Beatles fan. He didn't sing along, but he'd listen intensely