Whistle Duet

Today I was in a store and a woman started to whistle next to me. Next thing I know, a different woman started to whistle sort of the same tune, with a few added "hmm da dums" and "la dee das." I didn't recognize the tune. It was strange, yet compelling. I mean seriously, how often do two strangers whistle duet?

And now for your homework: whistle your favorite tune with a friend, report back later. Ready, go!