A Harmony Ball, also called Angel Caller or Bola Necklace in some cultures, typically is made from sterling silver and contains a small bell like item that emits very subtle but audible chimes with movement, not unlike the sound of wind charms in a very soft breeze.
Often worn by pregnant women, it is said that by 18-20 weeks, the developing baby starts to hear and be comforted by the sound of the bell.
Beautifully pairs with a Talis silver bead necklace (shown in picture, sold separately).