The lantern tower of Saint Sulpitius Church accommodates the historical Hemony-Sergeys carillon of Diest. In 1671, the city purchased a carillon from the famous Amsterdam bell-founder Pieter Hemony. He is to bells and carillons, what Stradivarius is to violins. This unique carillon with 32 bells is also the largest remaining Hemony carillon in the world. In 1974, some 15 bells from Jacques Sergeys were added to the carillon. That brought the total number of bells to 47.
Teun Michiels and Wim Van den Broeck are the city carillonneurs of Diest. Every year, an annual International Carillon Festival takes place in Diest during the summer months.