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. It can also be automated by machinery.

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".

Speed control of a tower bell is exerted by the ringer only when each bell is mouth upwards and moving slowly near the balance point; this constraint and the intricate rope manipulation involved normally requires that each bell have its own ringer. The considerable weights of full-circle tower bells also means they cannot be easily stopped or started and the practical change of interval between successive strikes is limited. This places limitations on the rules for generating easily-rung changes; each bell must strike once in each change, but its position of striking in successive changes can only change by one place.

Change ringing is practised worldwide, but it is by far most common on church bells in English churches, where it first developed. Change ringing is also performed on handbells, where conventionally each ringer holds two bells, and chimed on carillons and chimes of bells, though these are more commonly used to play conventional melodies.

Today, some towers have as many as sixteen bells that can be rung together, though six or eight bells are more common. The highest pitch bell is known as the treble, and the lowest is the tenor. In some towers, a bell larger than a tenor that is present would be called a bourdon. The bourdon is not part of the change ringing peal; it is hung from a pivoted beam. For convenience, the bells are referred to by number, with the treble being number 1 and the other bells numbered by their pitch—2, 3, 4, etc.—sequentially down the scale. (This system often seems counter-intuitive to musicians, who are used to a numbering that ascends with pitch.) The bells are usually tuned to a diatonic major scale, with the tenor bell being the tonic (or key) note of the scale. Some towers contain additional bells so that different subsets of the full number can be rung, still to a diatonic scale. For instance, many 12-bell towers have a flat sixth, which if rung instead of the normal number 6 bell allows 2 to 9 to be rung as light diatonic octave; other variations are also possible.

The bells in a tower reside in the bell chamber or belfry usually with louvred windows to enable the sound to escape.

The bells are mounted within a bellframe of steel or wood. Each bell is suspended from a headstock fitted on trunnions (plain or non-friction bearings) mounted to the belfry framework so that the bell assembly can rotate. When stationary in the down position, the centre of mass of the bell and clapper is appreciably below the centreline of the trunnion supports, giving a pendulous effect to the assembly, and this dynamic is controlled by the ringer's rope. The headstock is fitted with a wooden stay, which, in conjunction with a slider, limits maximum rotational movement to a little less than 370 degrees. To the headstock a large wooden wheel is fitted and to which a rope is attached. The rope wraps and unwraps on the rim of the wheel as the bell rotates backwards and forwards. This is full circle ringing and quite different from fixed or limited motion bells, which chime. Within the bell the clapper is constrained to swing in the direction that the bell swings. The clapper is a rigid steel or wrought iron bar with a large ball to strike the bell. The thickest part of the mouth of bell is called the soundbow and it is against this that the ball strikes. Beyond the ball is a flight, which controls the speed of the clapper. In very small bells this can be nearly as long as the rest of the clapper.

Below the bell chamber there may be one or more sound chambers, (one of which is likely to house the clock mechanism if the church has one) and through which the rope passes before it drops into the ringing chamber or room. Typically, the rope's length is such that it falls close to or on to the floor of the ringing chamber. About 5 feet (1.5 m) from the floor, the rope has a woollen grip called the sally (usually around 4 feet (1.2 m) long) while the lower end of the rope is doubled over to form an easily held tail-end.