Automatic round singer, first attempt: using "rest" -- FAIL. WHY: adding debugging vars shows that it's the Leader who's too slow. Playing 8 beats at tempo 120 should be 4 seconds = 120 frame ticks. CONFUSION: but precise timing diagnosis is confusing? A "play for 1 beat" block does not take 15 ticks to return control to the following timer block, but much less. Conjecture: the *next* "play" block must then perform the wait until the currently-playing note has ended. Switching the Leader's procedures to "run without screen refresh" seems to clean up the timing, though not perfectly. It still lags by like 0.3 beats over 8 beats ~= 4% slow.
