Rett syndrome (RTT) is a neurodevelopmental disorder found all over the world. The disorder affects basic body functions including the central control of the autonomic nervous system in the brainstem. Music seems to be extremely important to almost every person with RTT and is used by parents and carers in different situations, e.g. to calm down, to activate, to motivate and in communication. The importance of music for people with RTT has been documented in the literature. Dr Andreas Rett (Rett, 1966), who first described the syndrome, wrote about it as early as 1966. No study has been undertaken to examine more closely why music is so important, and how music physiologically affects people with RTT. Generally people with