Every object has a natural frequency at which it will vibrate when hit.

I Withdraw My Question (The Simpsons) (1:22 – watch first 0:40 only)

Tuning forks are metal objects designed to vibrate at a particular frequency. Tuning forks produce an exact sound tone that can used to tune an instrument.

Tuning Fork at 1600fps – The Slow Mo Guys (2:27 – start at 1:06)

The energy transmitted in a sound wave can be used to levitate drops of water in the air.

Water levitating by sound (0:57)

CYMATICS: Science Vs. Music – Nigel Stanford (5:52)

Music and Math. The Genius of Beethoven. (4:19)

Beethoven’s music is just kindergarten math 👶 (ft. John O’Conor) (0:55)