I’ve been using Muse for almost a year and recently, during the “Body” series, I noticed during a regular session a deeper “Ommmm-like” sound which appeared briefly as I seem to drop into a more focused brain state. It only occurred for about 10 seconds during this session. It didn’t appear the next session. Over the past month, I have been able to achieve this “Omm-like” sound about 30 seconds into the body meditation series and maintain it for longer and longer throughout the session. It seems there must be brainwaves that produce this special sound. Do other series have similar “levels” of sound that are unlocked during the achievement of certain patterns of brainwaves? Thanks in advance for clues.