Resonant strings

Sympathetic strings or resonance strings are auxiliary strings found on many Indian musical instruments, as well as some Western Baroque instruments and a variety of folk instruments. They are typically not played directly by the performer (except occasionally as an effect), only indirectly through the tones that are played on the main strings, based on the principle of sympathetic resonance. The resonance is most often heard when the fundamental frequency of the string is in unison or an octave lower or higher than the catalyst note, although it can occur for other intervals, such as a fifth, with less effect.

Sympathetic strings are used to enhance the sound of an instrument. Some instruments have only a few sympathetic strings such as the Hardanger fiddle (pictured right). Other instruments which have more include the sitar and sarod with 15 sympathetic strings, and the sarangi which has a total of 37 sympathetics. In Western music, some members of the viola family appeared in the middle of the 17th century which were fitted with an extra choir of thin wire strings running through a hollow chamber through the neck of the instrument, the head of which was then elongated to accommodate as many extra tuning pegs as necessary. These were generally called viola d'amore; another historical example is the baryton, for which Haydn wrote many trios. Other instruments such as the harp, lute, guitar, harpsichord and piano do not have additional strings, but make use of the effect by allowing their playing strings to vibrate sympathetically when they are not being played directly. In keyboard instruments like the piano, the string dampers can be raised to produce this effect.

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