Complete each sentence choosing the correct option
Standing bells originated in China. An early form called nao took the shape of a stemmed goblet, mounted with rim uppermost, and struck on the outside with a mallet. The manufacture and use of bowls specifically for 'singing' is believed to be a modern phenomenon. Bowls that were capable of singing began to be imported to the West from around the early 1970s. They are usually placed on a pillow, to allow the rim to vibrate freely, though small bells may be held gently in the hand.
Alternatively, some bells may be capable of 'singing bowl' operation as a friction idiophone. In this mode, a wooden mallet sometimes called a wand or puja is rotated around the outside rim to excite continuous vibrations in the bowl by the slip-stick mechanism, the principle being the same as that of water-tuned musical glasses. The volume of the continuous note depends on the speed of the mallet and the force that is applied.