Interesting...maybe I never heard it cause I had the other non-500 tank on the bike.Your motorcycle is 'singing' to you. The noise is quite normal.
Any guidance on why the motorcycle might have shut off under throttle? I'm guessing too much fuel at 3 turns out on both carbs (although I think the fuel/air mix screws only affect idle).
I'm planning on looking at the trouble shooting guide in Haynes manual as well.