The molten metal is then poured into a mold made up of a core, which is the shape of the inside section of the bell, and a cope, which is the shape of the outside of the bell. A bell's weight and profile , or shape, determine its note and the quality of its tone. Once cast, a bell must be tuned.
Most musical instruments produce a complex set of harmonically related overtones or partials.
A bell, on the other hand, produces a sound whose partial tones are not necessarily harmonically related. To produce a pleasing, harmonically related series of tones, the bell's profile is very carefully adjusted, or tuned, by the bell founder. Bell founders tune five principal tones of a bell. These are the Hum Tone , the lowest pitched partial, produced by the vibration of the entire bell. An octave above that is the Prime .