The "singing bowls" are traditionally constructed of a 7 metal alloy which when struck or rubbed produce a resonant humming tone. The use of instruments such as bells, cymbals, gongs, etc. in meditative practices and other rituals are quite common. Further the concepts of sound and vibration as the means of creation, transformation, etc. are common doctrinal features of Buddhism and Hinduism, and many other world religions, including the Judo-Christian tradition for that matter.
We hand select this bowls for tone; be careful with what you purchase...there can be a vast difference in quality with singing bowls. Look
HERE for more info.