What vibrates when a violin drum is a human voice?

When violins are played, the strings vibrate (along which the bow is drawn), which in turn cause the air to vibrate;

When a drum sounds, the drum membrane vibrates (which is beaten with a stick or other instrument), the vibrations of the membrane are transmitted to the air;

When a person’s voice sounds, his tongue vibrates (vibrations of the tongue cause nerve contractions from the brain), which also causes the air to vibrate.

As you can see above, in each case different objects vibrate (string, membrane, tongue), but they all transmit their vibrations to the air.