A carillon is a large, pitched percussion instrument that consists of from 23 to 77 suspended cast bronze bells housed in a bell tower that are tuned in chromatic order and struck with metal clappers that are connected to a keyboard and pedalboard. Carillons exist in a wide variety of appearances, sizes, weights and sound characteristics. They are among the world's heaviest musical instruments, with the largest weighing more than 91 metric tons. Carillons frequently have automatic controls that causes the bells to be struck periodically throughout the day to announce the time and play simple tunes. They are most commonly located in churches and universities.