Asni the Harper
Italian style baroque triple harp, 17th century (Simon Capp, 1996)
The designation "arpa doppia" first appears in Monteverdi's opera "L'Orfeo" (1607), where it is one of the instruments which provide interludes (ritornelli) to Orfeo's grand prayer "Possente Spirto", the centerpiece of the opera, in which the mythical singer begs the king of the Underworld to release his beloved Euridice. (listen to the harp verse here)
The instrument must have been in use in Italy for at least a decade then. Some of the earliest evidence comes from Naples, which at the time was under Spanish rule - and it may well be that the idea to build multi-row chromatic harps had drifted over from Spain, were such instruments seem to have been known since the mid-sixteenth century (see arpa de dos órdenes). The Neapolitan composer Giovanni Maria Trabaci wrote several pieces specifically for the harp, including his toccata seconda e ligature per l'arpa which was published shortly before 1600. Other Neapolitans who wrote for harp include Ascanio Mayone and Giovanni Maque.
The arpa doppia or baroque triple harp does not have a pedal or lever mechanism to change the pitch of the strings, like modern harps do - as the name "triple harp" implies, it has three parallel rows of strings. The outer two are tuned diatonically - usually in C major, although the historical tuning may have been F major or even B major. The middle row contains all the chromatic notes - like the black keys on a modern piano.
This makes the instument much better suited for music that shifts tonalities quickly, like much 17th century music does, and for continuo playing. It is rather difficult to play in keys with many accidentals in the key signature though - which is probably why it was superceded by the pedal harp by about the middle of the 18th century, when it had become established practice to regularly use all keys of the circle of fifths, rather than the more restricted range of tonalities that characterize most 17th century music.
"arpa doppia" is Italian for "double harp" - but the word seems to refer not so much to the multiple rows of strings, but rather to the harp's size: the harp used by Monteverdi and Trabaci has a range from contra G to e''' - a whole octave below the range of a standard gothic harp. The word may then have been used in the same way as today's "double bass", meaning an instrument that "doubles at the octave".
The baroque triple harp had its heyday in the early 17th century in Italy, when it was very popular as an accompanying instrument in the then newly developed "continuo" style. However, Italian style chromatic harps quickly spread over most of Europe, together with the Italian operatic style.
In Germany, it was known from Schütz's time, and lingered on well into the 18th century. Some late 17th century composers used it as an obligato instrument for their cantatas - among them Friedrich Wilhelm Zachow, Handel's first music teacher.
Handel himself has repeatedly written for the harp, both as an obligato instrument in some of his operas and oratorios (Giulio Cesare, Esther, Saul) and, of course, in his famous harp concerto.
The instrument he would have known, in early 18th century London, was probably similar to what survives to this day as a folk instrument in Wales - the Welsh triple harp, which follows the same general principle as the Italian triple harp, but has a somewhat different shape - a very high, curving neck and pillar, and a soundbox that widens out at the bottom, which makes for quite a different sound quality.
Listen to music performed on this harp: