Like most musical instruments, the harp has become louder, larger and more mechanical as it developed from simple medieval instruments with a dozen strings or less, to the modern, five and a half octave, double-action pedal harp.The enormous increase in string tension associated with the complex and heavy mechanism for altering the pitch of the strings makes the modern concert harp as different from its Baroque predecessors as the piano is from the harpsichord.
To modern eyes, medieval harps seem very small - small enough to be held on the player's lap, and with only about a dozen strings. This corresponds to the typical range of vocal music in this period - even when two voices sing together, they will typically both use the same register. The usual string material is gut, and the tuning is essentially diatonic - like the white notes of a keyboad. Medieval literature contains many references to harps, some of them making it clear that the instrument could be tuned in varied and subtle ways, and that the act of tuning was itself part of the performance.
Around the middle of the 14th century, we read of larger harps with around 24 strings. In 'Le Dit de la Harpe', the composer-poet Guillaume de Machaut compares the 25 graces of his Lady to the 25 strings of his harp. Part-music of this period tends to employ the alto-baritone range of pitches, and the usual tuning of this harp began at GG - the gamut, by convention the lowest note in vocal music.
There are very many pictures and even some surviving examples of the so-called 'Gothic' harp - a tall elegant instrument carved into pointed corners reminsicent of a Gothic arch. These Gothic harps were being played as late as the early 17th century, and players developed alternative tunings and finger-stopping techniques to create the illusion of chromatic notes (black notes on a keyboard).
It was the lack of a full chromatic compass that the theorist Juan Bermudo identified as the main 'defect' of the harp in the mid-16th century. His 'remedies' included tunings with 8 or 9 notes to the octave (more than the 7 'white' notes, but less than the full 12-note chromatic scale) and tunings adapted to each mode, with different accidentals in each octave. But he noted that some players had already added all the required strings: this was done by putting the 'black note' strings in a second row, that crossed over the main row in the way that your fingers interlock when you clasp your hands. This was called the 'arpa de dos ordenes' - the two-row harp.
Surviving instruments and pictures of 17th century Spanish harps show instruments that are very wide in the bass, although narrow in the treble. This shape, and the playing position (with the right hand plucking at the top of each string, while the left hand plays the string in the middle of its length) produce the characteristic sound of the Spanish harp: brilliant and clear in the treble, resonant and full in the bass.
!6th century Italian harps had much narrower sound-boards than Spanish harps of the same period: this may be why the Italians were forced to place the two rows of their double harp (arpa a due ordini) in parallel. In his 'Dialogo della musica', the theorist Vincenzo Galilei describes an arpa doppia with the strings in two parallel rows: 'white' notes in one row, 'black' notes in the other. The rows switch sides in the middle of the compass, so that in the treble the 'white' notes are on the right, but in the bass, they are on the left.
By around 1600, harps were made much larger, giving an extended bass range comparable to that of the chitarrone or theorbo (the double-bass member of the lute family). These larger harps had three rows of strings (arpa a tre ordini): 'white' notes in the outside rows (one row for each hand) and 'black' notes in the middle row. Nevertheless, these instruments were still called 'arpa doppia' - "double" here refers to the large size and bass range of the harp, rather than to the number of rows. This is the instrument for which Monteverdi wrote his famous solo in his opera 'L'Orfeo'.
The French theorist Mersenne mentions several harp virtuosi of international reputation in his 'Harmonie Universelle' of 1636. The Roman harpist Orazio Mihi was considered the equal of his contemporary, the harpsichordist Girolamo Frescobaldi. But the Frenchman Jean le Flesle played the triple harp 'en perfection'. Le Flesle was harpist to the English Queen and appeared in the court masque 'The Temple of Love' playing the role of Orpheus sitting in "a Barque of Antique design, adorn'd with a great masque head of a Sea-God; touch'd with silver and gold...the Barque moved gently on the Sea, heaving and setting and sometimes rowling" while Orpheus played to "calme the seas with his harp".
The Irish Harp was known throughout Europe as a distinct instrument, differing from the usual gut-strung harps in having thick brass wires, and being carved from a single massive willow tree-trunk, rather than having the box built up out of coopered ribs, like a lute-back. The characteristic shape of an Irish Harp is familiar from Irish coins and bottles of Guiness - the instrument is indeed a national symbol. It seems likely that even in the middle ages, Irish Harps had more strings than gut-strung harps, and it may have been the Irish harp that inspired the building of the first 24-string Gothic harps.
The 'Queen Mary' Harp in Scotland and the so-called 'Brian Boru' harp in Dublin are typical of late 15th and 16th century Irish harps with around 25-30 strings and a sound-box that is still small enough to rest on the player's lap. In the mid-17th century, some very large Irish harps were made with 40 strings or more, and some of these seem to have been chromatic. It was during this period that William Lawes wrote his famous 'Harp Consorts' for Irish harp, theorbo. violin and viol: the harpists of the King's private band of musicians (The Consorte) were all players of the Irish harp.
The typical Irish harp of the late 17th and 18th centuries was however rather smaller, with about 36 brass strings tuned diatonically in G major. This is the type of harp that was played by itenerant harpists such as Arthur O'Neill (whose instrument has survived to the present day) and the composer Turlough O'Carolan.
With the Restoration of Charles II, the Irish harpists were replaced by 'His Majesties harper for the Italian harp' - this was probably an imitation of French taste, since the Italian triple harp was the fashionable instrument in France. Handel's harp concerto and the solos in his operas and oratorios were written for the Welsh triple harp (derived from the Italian instrument, but with a cross-grain soft-wood soundboard). The Welsh triple harp survived as a folk instrument into the 20th century, although the later instruments are of very heavy construction, imitating the orchestral harp. In spite of the efforts of English benefactors, the Irish harp died out, and was revived only in drastically altered form as the neo-Irish or Celtic harp, an utterly modern instrument with high-tension nylon strings. There is now a revival of the wire-strung harp, especially in Ireland, Brittany and the USA, but modern steel strings and spun wires produce quite a different sound from the thick brass strings of the early Irish harps.
According to Baroque music dictionaries, German harpists knew three types of harp: the gut-strung double-harp (known as the Davidsharfe); the Irish harp and the arpanetta (Spitzharfe). This last is a kind of upright psaltery, with thin wire strings stretched over both sides of a triangular sound-box: the instrument is placed on a table, and played as if it were a harp, with one hand each side of the triangular frame. The arpanetta is the 'upright piano' of the Baroque period - a domestic instrument that was made and played all over Europe in great numbers, but for which no specific repertoire survives.
The ancestor of the arpanetta (and of the hammer dulcimer) was the psaltery, with thin wire strings stretched over a sound-box. The typical renaissance shape was the so-called 'pig's snout', in which the width of the soundboard increases steadily from the treble to the middle of the instrument, but is then constant in the bass. This shape is strongly suggestive of some kind of drone-tuning for the bass strings. The psaltery was particularly popular in Spain, where it was known as the 'quanun':some 17th century settings of dance tunes for psaltery survive in manuscript.