bourdon

Bells separated from the next higher note by more than two semitones (one whole tone) are called sub-bourdons.

The deep, resonant tone of a bourdon is used to mark hours, call to prayer, and solemnize major national or religious events like funerals, royal celebrations, or the end of wars, adding majesty and historical significance to bell towers and churches.

As an example, the largest bell of a carillon of 64 bells, the sixth largest bell hanging in the world, in the Southern Illinois town of Centralia, is identified as the 'bourdon.' It weighs 11,000 lb and is tuned to G. In the Netherlands where carillons are native, the heaviest carillon is in Grote Kerk in Dordrecht (South Holland). The biggest bell serving as bourdon of any carillon is the low C bell at Riverside Church, New York City. Cast in 1929 as part of the Rockefeller Carillon, it weighs 41,000 lb and measures 10 ft across. The bourdon at St. Paul’s Cathedral in London, called Great Paul, weighs 16.7 tonnes. It is the largest bell ever cast in the British Isles. Great Paul is the second heaviest bell in the United Kingdom after the 25.7 tonnes Olympic Bell, cast in the Netherlands for the 2012 London Games. As it is not a part of a harmonically-tuned set, the Olympic Bell is not considered a bourdon. Some cathedrals can have more than one bourdon bell. For example Notre-Dame de Paris has two bourdon bells, named Marie and Emmanuel which are hung in the south tower.

The heaviest bell in a diatonically tuned English-style ring of bells (change ringing) is called the tenor. If a larger, heavier bell is also present it would be called a bourdon. The bourdon is not part of the change ringing peal; instead, it is hung from a pivoted beam and is typically only used to sound the hour or for other civic and religious purposes.