If you grasp Tibetan Singing Bowls in your hand, it stays free to vibrate. Then, you can softly glide a mallet across the side of it. This is what causes the singing sensation, often used for Tibetan meditation. You can also quietly tap the side of the bowl. This makes a bell-like noise. Either method you use crystal singing bowls, it is the vibrations that generate the sound, like if you glide your finger around the edge of a goblet. The pitch of the singing can be changed depending on the bowl density. Bowls can range in diameter from six to 15 inches. You can also increase the mallet spin rate to modify the sound.