Hello, friend. I don't know much. There is a Redditor, Little_Acanthaceae who is an amazing science-based poster on the r/stutter site. This person is a stutterer who has dissected the medical aspects of our disorder. Go to my site to find what I've accessed from this person. About the rhythmic tapping. It seems that few of us have the outward manifestation of the tapping but experience a defect in our ability to copy, follow, tapping we hear. Are you on the outward expression side like I am? If Google rhythmic tapping stuttering there isn't much and its pretty scientific, however, it does indicate that our condition is physiological as well as psychological. I'd like to chat. Hood luck.