What is "crystal singing" in Crystal Line?

Crystal Line was written by Anne McCaffrey. It is a story about a woman named Killashandra Ree, who joins the Heptite Guild to become a crystal singer. Crystal singing is singing the frequencies of the gem deposits buried on the planet Ballybran. The song of the crystal is a powerful force that captivates the attention of Guild Master Lanzecki. Crystal singing afforded Killashandra enjoyment, near-eternal life, and memory loss. However, she felt intense loneliness from her heart still remembering what her mind forgot over time.
Killashandra is a talented crystal singer. She becomes very rich from using her talent to her own advantage. Her body has a need for crystal. The Guild Master manages the group's affairs, so he doesn't crave the crystal, since he does not want to lose his memory and risk not being able to do his job. Killashandra finds herself involved in undertakings that restructure the activity of the crystal singers at the direction of the Guild Master.