That’s it – start things off by just listening. It’s important to remember that this is supposed to be a fun activity; don’t make it too serious or boring.
As an alternative, you can show a video clip if you have one – in fact, I strongly recommend it, as it will cater to more learners’ needs in terms of learning styles (visual and audible).
Ask learners if they’ve heard it before, and don’t overload them with tasks at this point; simply let them enjoy the music.