If you grip Tibetan Singing Bowls in your hand, it stays free to vibrate. Then, you can softly glide a mallet along the side of it. This is what makes the singing noise, often used for Tibetan meditation. You can also quietly hit the side of the bowl. This makes a bell-like chord. Either way you use crystal singing bowls, it is the vibrations that make the sound, similar to if you glide your finger around the edge of a champagne glass. The pitch of the sound can be changed depending on the bowl depth. Bowls can range in diameter from six to 15 inches. You can also increase the mallet spin rate to alter the sound.