Aliquot stringing
Aliquot stringing is the use of extra, un-struck strings in a piano for the purpose of enriching the tone. Aliquot systems use an additional (hence fourth) string in each note of the top three piano octaves. This string is positioned slightly above the other three strings so that it is not struck by the hammer. Whenever the hammer strikes the three conventional strings, the aliquot string vibrates sympathetically. Aliquot stringing broadens the vibrational energy throughout the instrument, and creates an unusually complex and colorful tone.
Etymology[edit]
The word aliquot ultimately comes from a Latin word meaning 'some, several'. In mathematics, aliquot means 'an exact part or divisor', reflecting the fact that the length of an aliquot string forms an exact division of the length of longer strings with which it vibrates sympathetically.
Other musical instruments[edit]
Makers of other string instruments sometimes use aliquot parts of the scale length to enhance the timbre. Examples of such instruments include the viola d'amore, and the sitar.