Have you ever noticed that what your ribs and diaphragm and chest do are quite similar both in sobbing and laughing? Both are cathartic releases of emotion.
I am increasing inclined to view the root repository of tension and anxiety as the intracostal muscles and the diaphragm. It is for this reason that deep breathing over a long period, as in Wholotropic Breathwork, stimulates and releases emotions, when it happens in a supportive environment.
I will add, too, that I think what the breathwork does is get you into a space without movement–a trauma, or perhaps even a mystical experience–and then add movement, through the evolution of music.
I may have made that comment earlier, but can’t remember.