<P> At the other end of its vibrating length, the string passes over the bridge, another sharp edge made of hardwood . As with the nut, the horizontal position of the string along the bridge is determined by a vertical metal pin inserted into the bridge, against which the string rests . The bridge itself rests on a soundboard, a thin panel of wood usually made of spruce, fir or--in some Italian harpsichords--cypress . The soundboard efficiently transduces the vibrations of the strings into vibrations in the air; without a soundboard, the strings would produce only a very feeble sound . A string is attached at its far end by a loop to a hitchpin that secures it to the case . </P> <P> While many harpsichords have one string per note, more elaborate harpsichords can have two or more strings for each note . When there are multiple strings for each note, these additional strings are called "choirs" of strings . This provides two advantages: the ability to vary volume and ability to vary tonal quality . Volume is increased when the mechanism of the instrument is set up by the player (see below) so that the press of a single key plucks more than one string . Tonal quality can be varied in two ways . First, different choirs of strings can be designed to have distinct tonal qualities, usually by having one set of strings plucked closer to the nut, which emphasizes the higher harmonics, and produces a "nasal" sound quality . The mechanism of the instrument, called "stops" (following the use of the term in pipe organs) permits the player to select one choir or the other . Second, having one key pluck two strings at once changes not just volume but also tonal quality; for instance, when two strings tuned to the same pitch are plucked simultaneously, the note is not just louder but also richer and more complex . </P> <P> A particularly vivid effect is obtained when the strings plucked simultaneously are an octave apart . This is normally heard by the ear not as two pitches but as one: the sound of the higher string is blended with that of the lower one, and the ear hears the lower pitch, enriched in tonal quality by the additional strength in the upper harmonics of the note sounded by the higher string . </P> <P> When describing a harpsichord it is customary to specify its choirs of strings, often called its disposition . Strings at eight foot pitch sound at the normal expected pitch, strings at four foot pitch sound an octave higher . Harpsichords occasionally include a sixteen - foot choir (one octave lower than eight - foot) or a two - foot choir (two octaves higher; quite rare). When there are multiple choirs of strings, the player is often able to control which choirs sound . This is usually done by having a set of jacks for each choir, and a mechanism for "turning off" each set, often by moving the upper register (through which the jacks slide) sideways a short distance, so that their plectra miss the strings . In simpler instruments this is done by manually moving the registers, but as the harpsichord evolved, builders invented levers, knee levers and pedal mechanisms to make it easier to change registration . </P>

The harpsichord was used as an accompanying instrument in opera only in the 16th century