According to Tibetan tradition, the existence of singing bowls dates back to the time of the historical Gautam Buddha Shakyamuni (560 – 480 B.C.).
The tradition was brought from India to Tibet, along with the teachings of the Buddha, by the great tantric master Padmasambhava in the 8th century A.D.
Singing bowls produce a great sound which invokes a deep state of relaxation which naturally assists one in entering into meditation, the ultimate goal being enlightenment.
They are a quintessential aid to meditation and can be found on private Buddhist altars, and in temples, monasteries and meditation halls throughout the world.
The original analysis we know of from Concordia University, Quebec is an eight-metal alloy of copper and tin with traces of iron, lead, Brass, zinc, gold, silver, and mercury.
In addition to their traditional usage for meditation, Tibetan singing bowls are used for deep Therapy, relaxation, stress reduction, holistic healing, Reiki, chakra balancing, and World music.
Many people find that the rich blend of harmonic overtones which the bells produce have a direct effect upon their chakras.
Playing the bells usually causes an immediate centering effect. The tones set up a “frequency following response” that creates a balancing left/right brain synchronization.
Meditating on the subtle sounds of the Tibetan singing bowl tunes one into the universal sound within and without. With Great work, you can see the Outcomes. Antique Singing Bowl Old Ultibati

All the recording of the Singing Bowl you can check in the youtube video link given below. Clearly Shown in the picture (picture gives a better clarity along with the video).

According to the sound of a different singing bowl, it has highly used for Relaxation purpose and also used for Music Meditation. The Hand-Hammered is represented as the best bowl for Healing Chakra Meditation in the world.

Authentic Singing Bowl Giant Ultibati

Large Giant Highwall Ultibati

Giant Single Large Ultibati Singing Bowl