Can you play your ribs like a xylophone?

Answer 1

No, you cannot.

In order for a xylophone to work, or any such percussion instrument, metal bars vibrate when struck, and the vibrations resonate to create the sound. The length of the bar determines the pitch of the sound.

Your ribs, however, are made of softer material (hydroxyapaptite bone with marrow in between), and are bound to tendons and ligaments, and other such soft tissue, which would prevent the vibrations from resonating properly.

So, at best, striking a bone within the body would create a thud sound, rather than the ping of a xylophone.