Where you are missing the point is that in those endeavors you mention—music, acting, sports—the activity IS play. Playing is what you are expected to be doing,

Where you are missing the point is that in those endeavors you mention—music, acting, sports—the activity IS play. Playing is what you are expected to be doing, and you actually practice at it. (Source: I majored in acting and music.) Certainly Cleese is more interested in the creativity of ideas, especially writing, but his requirements for creativity (space, time, time, confidence, humor) apply to anything.