Time rings (outer, cool) strike on the real boundary — the hour ring on the hour, the 20-second ring at :00, :20, :40, the second ring every second. Everything lands together on the minute, and the whole field lands on the hour. Musical rings (inner, warm) run against the bar at your tempo: a ring of 5 fits five strokes into every bar, whatever the bar is. Turn a ring on by tapping it, or from the lists.