The Six Healing Sounds or Liu Zi Jue (六字訣) is one of the common forms of Chinese qigong, and involves the coordination of movement and breathing patterns with specific sounds.
The Term Liu Zi Jue first appears in a book called On Caring for the Health of the Mind and Prolonging the Life Span written by Tao Hongjing of the Southern and Northern Dynasties (420 - 589). A leading figure of the Maoshan School of Taoism, Tao was renowned for his profound knowledge of Traditional Chinese Medicine. "One has only one way for inhalation but six for exhalation" he writes in the book.
Zou Pu'an of the Song Dynasty (960 - 1279) was a major contributor in terms of theory and practice to the transmission of the exercise through his book The Supreme Knack for Health Preservation - Six-Character Approach to Breathing Exercises.
No body movements accompanied the Liu Zi Jue exercises until the Ming Dynasty (1386 - 1644) when Hu Wenhuan and Gao Lian wrote books on the subject. For instance they both included in their books the summary of Liu Zi Jue for dispelling diseases and prolonging the life span, which combines controlled breathing with physical exercises.