Sometimes I'll sit down at the piano and start playing in the second lowest octave "Eb G Ab A Bb." I'll say to someone "try playing just the black keys." They'll poke at them a bit, and it tends to sound something like this:

Eb-blues.mp3

This isn't amazing music or anything, but it can get someone who doesn't know what to do with an instrument sitting at a piano and figuring out what the keys do. It's a nice place to start.

(This works because the black keys on the piano make a minor pentatonic scale in Eb, and that's a common scale for improvising in a blues context.)

(As with everything in casual music, it's all about interest management. In this case the goal is to give someone an easy learning curve where they can start with "this is kind of music!" and continually feel the process of getting better.)