Change ringing is the art of ringing a set of tuned bells in a tightly controlled manner to produce precise variations in their successive striking sequences, known as "changes". This can be by method ringing in which the ringers commit to memory the rules for generating each change, or by call changes, where the ringers are instructed how to generate each change by instructions from a conductor. This creates a form of bell music which cannot be discerned as a conventional melody, but is a series of mathematical sequences.
Change ringing originated following the invention of English full-circle tower bell ringing in the early 17th century, when bell ringers found that swinging a bell through a much larger arc than that required for swing-chiming gave control over the time between successive strikes of the clapper. Ordinarily a bell will swing through a small arc only at a set speed governed by its size and shape in the nature of a simple pendulum, but by swinging through a larger arc approaching a full circle, control of the strike interval can be exercised by the ringer. This culminated in the technique of full circle ringing, which enabled ringers to independently change the speeds of their individual bells accurately to combine in ringing different mathematical permutations, known as "changes".
In change ringing where the order the bells are struck in is constantly altered, it is necessary to time the swing so that this strike occurs with precise positioning within the overall pattern. Precision of striking is important at all times. To ring quickly, the bell must not complete the full 360 degrees before swinging back in the opposite direction; while ringing slowly, the ringer waits with the bell held at the balance, before allowing it to swing back. To achieve this, the ringer must work with the bell's momentum, applying just the right amount of effort during the pull that the bell swings as far as required and no further. This allows two adjacent bells to reverse positions, the quicker bell passing the slower bell to establish a new pattern. Although ringing up certainly involves some physical exertion, actual ringing should rely more on practised skill than mere brute force. Even the smallest bell in a tower is much heavier than the person ringing it. The heaviest bell hung for full-circle ringing is in Liverpool Cathedral and weighs 82 long cwt 0 qr 11 lb (9,195 lb or 4,171 kg). Despite this colossal weight, it can be safely rung by one (experienced) ringer.
The simplest way to sound a ring of bells is by ringing rounds. This is a repeated sequence of bells descending from the highest to lowest note, which is from the lightest to the heaviest bell. This was the original sequence used before change ringing was developed, and change ringing always starts and ends with this sequence.
Most ringers begin their ringing career with call change ringing; they can thus concentrate on learning the physical skills needed to handle their bells without needing to worry about "methods". There are also many towers where experienced ringers practise call change ringing as an art in its own right (and even exclusively), particularly in the English county of Devon.
Call change ringing requires one ringer to give commands to change the order of the bells, as distinct from method ringing, where the ringers memorise the course of bells as part of a continuous pattern.
In call change ringing each different sequence of the bells, known as a "row", is specifically called out by one ringer, the "conductor", who instructs the other ringers how to change their bells' places from row to row. This command is known as a "call".
In method ringing, plain hunt is the simplest form of generating changing permutations in a continuous fashion, and is a fundamental building-block of many change ringing methods. The accompanying diagram shows plain hunt on six bells. The course of two bells only are shown for clarity. Each row in the diagram shows the order of striking after each change.
Some handbell change ringers practice a hybrid of these two methods, known as body ringing: ringers standing in a line each hold one bell, exchanging places in the line so that the changes sound correctly when the bells are rung in sequence from right to left.
Throughout the years since, the group theoretical underpinnings of change ringing have been pursued by mathematicians. "Changes" can be viewed as permutations; sets of permutations constitute mathematical groups, which in turn can be depicted via so-called Cayley graphs, which in turn can be mapped onto polyhedra. 
Bells have been installed in towers around the world and many rings in the British Isles have been augmented to ten, twelve, fourteen, or even sixteen bells. Today change ringing is, particularly in England, a popular and commonplace sound, often issuing from a church tower before or after a service or wedding. While on these everyday occasions the ringers must usually content themselves with shorter "touches", each lasting a few minutes, for special occasions they often attempt a quarter-peal or peal, lasting approximately 45 minutes or three hours respectively. If a peal attempt succeeds, towers sometimes mark the occasion with a peal board mounted on the wall of the ringing chamber; at St Peter Mancroft in Norwich there is one documenting what is generally considered to have been the first true peal: 5040 changes of Plain Bob Triples (a method still popular today), rung 2 May 1715. There is some evidence there may have been an earlier peal (also Plain Bob Triples), rung January 7, 1690 at St Sepulchre-without-Newgate in the City of London by the Ancient Society of College Youths. Today over 4000 peals are rung each year.
The Central Council of Church Bell Ringers, founded in 1891, is dedicated to representing change ringers around the world. Most regional and local ringing guilds are affiliated with the council. Its journal, The Ringing World, has been published weekly since 1911; in addition to news and features relating to bellringing and the bellringing community, it publishes records of achievements such as peals and quarter-peals. Ringers generally adhere to the Council's rules and definitions governing change ringing.
Methods of change ringing are named for the number of working bells, or the bells that switch order within the change. It takes a pair to switch, and commonly the largest bell (the tenor) does not change place. For example, there may be six bells, only five of which work, allowing for only two pairs. A method of ringing for these bells would be called doubles. Doubles is the most common group of methods rung in the United Kingdom, since the majority of parish churches with bell towers in the UK are fitted with only six bells.
In 2016 readers of The Ringing World magazine wrote to insist that bell ringing was "an art and a sport", as demonstrated by regular "striking competitions". It was suggested that classification of change ringing as a sport by Sport England could save it from becoming obsolete. But the Central Council of Church Bell Ringers opposed the move, suggesting that it would jeopardise its relationship with church bodies, since bell ringing should be seen as part of Christian worship, not exercise. The council's president, Chris Mew, said: "Where is the glamour of the sports field and where are the David Beckhams of the belfry?"
The COVID-19 pandemic made it impossible for bell ringers to assemble in belfries. Searching for alternative methods, in March 2020 two ringers from the USA developed software called Ringing Room that mimics the operation of ropes and bells, and permits people to ring together online, in a type of networked music performance. Various other online platforms for virtual change ringing have also been created, but Ringing Room is the most popular, with over 10,000 people joining in the first year.
The mystery novel The Nine Tailors by Dorothy L. Sayers (1934) contains a great deal of information on change-ringing. Her fictional detective, Lord Peter Wimsey, demonstrates his skill at ringing, and the solution to the central puzzle of the book rests in part upon his knowledge of the patterns of change ringing.
Connie Willis, who frequently references Sayers in To Say Nothing of the Dog (1997), features bell ringers in her earlier novel Doomsday Book (1992); a group of American women led by a Mrs. Taylor frequently appears practising for or ringing both handbells and changes.
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