To state something over and over again in different ways. It comes from the art of bell ringing, which first came into popularity in the seventeenth century. A “change” means the order in which a series of bells are rung.
Thus, with a series of 4 bells, as in the Westminster chimes, it is possible to ring 24 changes without once repeating the order in which the bells are struck.
With 5 bells, 120 changes can be rung, for the variety increases enormously with the increase in the number of bells. With 12 bells, the greatest number used in change ringing, the huge figure of 479,001,600 changes is possible, possible, but not probable.
The greatest number ever actually rung upon church bells is reported to have been 16,000 changes, and this took somewhat more than nine hours, and the physical exhaustion of the ringers.
All the possible changes with any series of bells constitutes a “peal,” but when we use the expression in the figurative sense, we convey the idea of repetition ad nauseum by saying, “She rang all the changes.”