The Evolution of Modern Bells

Musical bells of an almond shaped plan (called nau) have been known in China since the SHANG Dynasty from the 15th century century BC and are found as musically tuned sets from the CHOU dynasty (1027 to 256 BC) during which both Taoism and Confucianism were founded and the use of bells a heightened part of courtly life.

Large, round (or axis-symmetric) bells are believed to have evolved in India and found a place in the traditions and rituals of Hinduism and later, Buddhism. This tradition made its way gradually through the nomadic steppes tribes into China from the fall of the HAN dynasty in 220 AD and the division of China into warring parts. Buddhism began to replace Confucianism as the state religion. While the bell, as an important religious object, languished in India under the long reign of Islam from the 2nd Century AD, in Buddhist China the single axis-symmetric bell grew in both scale and significance. The consolidation of China under the T'ANG dynasty from 620 AD consolidated the Buddhist bell in China. We have no significant Buddhist bells in China which predate the sixth century. This use of a single bell as a religious instrument relegated the Chung pein, a set of tuned bells used as a musical instrument, to a small part of the tradition of the temple. The technology of casting larger and larger bells swept through Korea and China, and then spread, in the same century, from Korea into Japan along with the Buddhist faith.

Very little information is available on aesthetic values pertaining to the sound of Asian temple bells and how these bells may have evolved in relatively recent times. Australian Bell has established a data base of Asian bell sounds and profiles, but much more detailed investigations including interviews with monks who use these bells, will need to be done before more systematic knowlege can emerge.

Ancient Chinese 2-tone musical bells	A Korean temple bell	A Korean temple bell spectrum

The European bell tradition is thought to have begun in the ancient Middle East with crotal bells and small clappered bells used on clothing and horse harnessing to protect the wearer from evil spirits. Large cast bronze bells have been known in churches since the early medieval times of Charlemaine in Europe. This art was largely confined in use to the rituals of the Christian religion. The art of casting bronze bells was a monastic practice until the late renaissance when in both Continental Europe and England a growing musical interest in the bell promoted the development of groups of bells into musical instruments. This growing secular appreciation of the bell as a musical instrument took the form of change ringing the swinging bell in England, and the construction of a keyboard (clavier) to mechanically play bells in a carillon in the Low Countries. The invention of the carillon in the mid 1500's AD, especially encouraged an interest in controlling more exactly the tuning of the individual bell and the tuning relationship between a group of bells. In Flanders during the 1630's a court musician Van Eyck, worked with the Hemony Brothers bellfounders to produce the first well-tuned musical bells for use in carillons.

The Hemony Brothers were able to distinguish and tune the first three overtones of their bells. They were able to tune the second overtone to twice the frequency of the fundamental, but the third overtone could only be tuned to the musical interval of a minor third (2.4 times the frequency of the fundamental).

The secret of tuning bells became gradually lost after the death of the Hemony bellfounders. It was rediscovered around the early 1890's when a bell enthusiast, Cannon Simpson worked with the English bellfounders, Taylors at Loughborough. The secret was not to try and cast a bell in tune (called a maiden casting if successful) but to cast the bell thicker than was required and using a lathe to cut away metal from inside the bell until the overtones were sounding in their proper tuned sequence of the first five overtones of the bell at frequencies 2, 2.4, 3 and 4 times the fundamental. This produced bells with a strong pitch perception based on the fundamental. However the minor third overtone has a large amplitude and Terhardt, in his paper on pitch perception, reported that in about 30% of trials people reported the pitch of a European bell to be the minor third overtone.

The minor third overtone was also a problem for carillons because it produced strong dissonances with the overtones of a bell playing at an interval of a major third. This is the second most common interval in Western music, so in the 1980's a Dutch foundry, Eisbouts, collaborated with Dr Schoofs from Eindhoven Technical University to design a bell with a major third overtone instead of the minor third. This was achieved by using a new computer modeling technique called Finite Element Analysis (FEA) to predict the frequencies of the overtones of computer models of bell with varying shapes.

In 1999 Australian Bell was commissioned by the Melbourne International Festival of the Arts to design and manufacture a set of large bells to comemorate the centenary of Australia's Federation. These bells were designed using very recent FEA with shape optimisation software (ReShape) produced by Advea Engineering. The world's first harmonic bell with seven partials in an harmonic series, along with a series of bells producing two and even three clearly perceived pitches, were designed and cast for this commission.

A harmonic bell	A harmonic bell spectrum