If you made first contact, and the aliens wanted you to demonstrate what music is, what would you sing for them?
I’m not proposing that such beings wouldn’t be advanced enough to pick up our radio signals, just that they wouldn’t have a concept of music. Let’s assume that they have a sense of hearing which approximates our own.
A few things to keep in mind: you’ll probably want to pick something more verse-based – musical interludes don’t tend to come across well in humming or whistling. I guess you could skip to the next verse, but I find this difficult to do spontaneously, myself.
Also – you’re representing all of Earth’s music here! Can’t just be reaching for any old song…