Bell tones are sounds played by instruments that are not bells, but that imitate the sound of bells by controlling the volume of the sound. Generally, this means that a sound is attacked hard, like a bell being hit, then sustained with a gradual decrescendo, like a struck bell slowly sounding out. It is a common technique used in many types of music, particularly orchestral and jazz music. Along with notation on paper to tell a musician to play bell tones, the conductor in a musical group usually gives hand signals that also guide the musicians in producing the bell tone sound.
In notation, bell tones are generally written with an accent above the initial note with a decrescendo that extends for the life of the note. Though the technical term for the accent used to indicate a hard attack on a note is a vertical accent mark, musicians sometimes refer to the accent playfully as a carrot. If the bell tones are longer than a single measure, they are indicated by multiple notes indicating the length of the note that are bound together by a tie. A tie is a curved line that goes from one note to the next to indicate that they are to be played in continuation without pausing between them. It looks somewhat like a half-parentheses over the notes.
Another important part of producing a bell-like tone is the decrescendo. On paper, a decrescendo is a symbol that looks like a stretched out greater-than symbol, starting open at one end, then gradually narrowing to a point. The narrowing of the decrescendo indicates a reduction in intensity or volume of the bell tones, and usually extends for the length of the note. In contrast, a crescendo looks like a stretched out less than symbol, and directs the musician to increase the sound intensity at the indicated rate. Generally, a director uses hand signals to guide a musical group in performing the decrescendos and accents that make up bell tones.
In music, bell tones are used not only to simulate the sound of bells, but also to guide instruments when they are playing the same melody as bells. This helps ensure a uniform sound that communicates the intended sound, which is meant to emulate the striking and reverberation of bells. Composers use this technique to simulate church or holiday bells, and it makes a frequent appearance in Christmas-themed instrumental pieces.