HARP (Fr. harpe; Ger. Harfe; Ital. arpa), a member of the class of stringed instruments of which the strings are twanged or vibrated by the fingers. The harp is an instrument of beautiful proportions, approximating to a triangular form, the strings diminishing in length as they ascend in pitch. The mechanism is concealed within the different parts of which the instrument is composed, (1) the pedestal or pedal-box, on which rest (2) the vertical pillar, and (3) the inclined convex body in which the soundboard is fixed, (4) the curved neck, with (5) the comb concealing the mechanism for stopping the strings, supported by the pillar and the body.
(1) The pedestal or pedal-box forms the base of the harp and contains seven pedals both in single and double action harps, the difference being that in the single action the pedals are only capable of raising the strings one semitone by means of a drop into a notch, whereas with the double action the pedals, after a first drop, can by a further drop into a second and lower notch shorten the string a second semitone, whereby each string is made to serve in turn for flat, natural and sharp. The harp is normally in the key of C flat major, and each of the seven pedals acts upon one of the notes of this diatonic scale throughout the compass. The choice of this method of tuning was imposed by the construction of the harp with double action. The pedals remain in the notches until released by the foot, when the pedal returns to its normal position through the action of a spiral spring, which may be seen under each of the pedals by turning the harp up.
(2) The vertical pillar is a kind of tunnel in which are placed the seven rods worked by the pedals, which set in motion the mechanism situated in the neck of the instrument. Although the pillar apparently rests on the pedestal, it is really supported by a brass shoulder firmly screwed to the beam which forms the lowest part of the body, a connexion which remains undisturbed when the pedal box and its cover are removed.
(3) The body or sound-chest of the harp is in shape like the longitudinal section of a cone. It was formerly composed of staves joined together as in the lute and mandoline. Erard was the first to make it in two pieces of wood, generally sycamore, with the addition of a flat soundboard of Swiss pine. The body is strengthened on the inside, in order to resist the tension of the strings, by means of ribs; there are five soundholes in the back, which in the older models were furnished with swell shutters opened at will by the swell pedal, the fourth from the left worked by the left foot. As the increase of sound obtained by means of the swell was infinitesimal, the device has now been discarded. The harp is strung by knotting the end of the string and passing it through its hole in the centre of the soundboard, where it is kept in position by means of a grooved peg which grips the string.
(4) The neck consists of a curved piece of wood resting on the body at the treble end of the instrument and joining the pillar at the bass end. In the neck are set the tuning pins round which are wound the strings.
(5) The comb is the name given to two brass plates or covers which fit over both sides of the neck, concealing part of the mechanism for shortening the strings and raising their pitch a semitone when actuated by the pedals. On the front plate of the comb, to the left of the player, is a row of brass bridges against which the strings rest below the tuning pins, and which determine the vibrating length of the string reckoned from the peg in the soundboard. Below the bridges are two rows of brass disks, known as forks, connected by steel levers; each disk is equipped with two studs for grasping the string and shortening it. The mechanism is ingenious. When a pedal is depressed to the first notch, the corresponding lower disk turns a little way on a mandrel keeping the studs clear of the string. The upper disk, set in motion by the steel levers connecting the disks, revolves simultaneously till the string is caught by the two studs which thus form a new bridge, shortening the vibrating length of the string by just the length necessary to raise the pitch a semitone. If the same pedal be depressed to the second notch, another movement causes the lower disk to revolve again till the string is a second time seized and shortened, the upper disk remaining stationary. The hidden mechanism meanwhile has gone through a series of movements; the pedal is really a lever set upon a spring, and when depressed it draws down the connecting rod in the pillar which sets in motion chains governing the mandrels of the disks.
The harp usually has forty-six strings, of gut in the middle and upper registers, and of covered steel wire in the bass; the C strings are red and the F strings blue. The compass thus has a range of 6½ octaves from
. The double stave is used as for the pianoforte. The single action harp used to be tuned to the key of E♭ major.