As the sun set over the Pacific Ocean, the beach cool against my back, a voice invited me to scan my body for feelings of powerlessness. “Then breathe in that area to help it release,” said Sara Sofia Bousiali, the leader of the evening’s sound bath.

Along with 21 other participants lying on the sand in Santa Monica this April, I listened as Ms. Bousiali played crystal singing bowls and chimes and guided us in an hourlong meditation. At the sound baths I’ve attended, the bell-like sounds seemed to fill my body and melt away racing thoughts. I lost track of time.

Therapeutic sound “baths” have been around for a few decades, said Jamie Bechtold, the co-founder and owner of a sound bath studio in Los Angeles. But she has seen…