The meaning of relaxation in a Tai Chi context is often confused with the same kind of limp, collapsed, let-go feeling you get from flopping on to the couch after a long day. In fact, there’s a very different sense of “song” or relaxation in Tai Chi, which is at once easy and loose, but also energized and alert. In his translator’s introduction to Mastering Yang Style Taijiquan, Louis Swaim nails the nuance of the concept.