Change ringing is a style of church bell ringing started in England around the end of the sixteenth century. Because of constraints imposed by the physics of swinging bells, tunes are not played. Instead, the bells are rung in ever changing patterns to a steady rhythm. Change ringing, while an obscure art, remains as widely practiced today as at any time in the past, and continues to evolve. The largest concentration of interest remains in England, which is home to over 95% of the world's bells hung for change ringing, with many of the remainder in other parts of the UK. However, there are small pockets in other parts of the world, mostly former British colonies, including Australia, Canada, Ireland, New Zealand, South Africa, the United States, and Zimbabwe. The past few decades have seen an increase in interest, with the number of towers outside the UK roughly doubling since about 1960. This category is for sites having to do with any aspect of change ringing.