Resonance in singing bowls is a relationship between vibrational frequencies, amplitude, and time which can be incredibly complex and yet is able to be described with mathematical equations and displayed graphically. Singing bowl resonance is something that you feel and appreciate regardless of your understanding of the complex relationships underlying it.
Sometimes the resonance of singing bowls played together with mallets or strikers will produce tones that each individual singing bowl does not have. Big premium quality Jambati style singing bowls are the easiest ones to experience resonance with, though any pair of singing bowls can have this feature. One of the great pleasures of having a singing bowl collection is to play with your pieces and see which ones really go together. Take it as a gift if it shows up in a group of bowls you have or buy.
Singing bowls that are close in tone will sometimes set one another off (ring one and silence it and you can hear the other faintly ringing). Even if the singing bowls don’t set each other off playing two or three singing bowls that are close in tone produces a nice effect.
You often get an augmentation of the main tone and a pulsing as the singing bowl motions increase and decrease the amplitude of the sound wave.
An important distinction with the bowls is that they are able to stand on their own and be complete in the fullness of their solo tones. Ultimately they are about sound, not music. Music works by engaging our brain’s sequence recognition circuitry, your brain knits together different sounds separated by time. Sound operates on a simpler, more primal level, that does not excite the intellect. It is by being perceived on these deeper levels that the singing of the bowls feels so good to so many different people in very different cultural contexts.