Well, one thing we're quite sure of though, and that is he has a very good listening ear and can catch beats and rhythm pretty well. Sometimes when he hears upbeat music and starts dancing, he'll hit his thighs with both hands along with the beat.
For now, Caleb has been exposed to Daddy's guitar. He loves running into Daddy's study whenever he gets a chance to pluck at the guitar strings. And I must say he plucks quite well for a 15 month old. See video below and if you listen carefully, you can hear him say "guitar"
And here's Caleb hitting away on drums at Uncle Darius' house

And here's Caleb with his keyboard. Just switch on the demo music and you'll see him swinging into action with his dance
