HARPSICHORDS
This very unusual item (showing left) is probably the world's oldest surviving stringed keyboard instrument – an upright harpsichord thought to have been made in Ulm circa 1480. Very few pieces of wooden furniture survive more than five hundred years so this is by any reckoning an extremely rare item. The gift of Sir George Donaldson in 1894, it is preserved in the museum of historic instruments at the Royal College of Music in London (opposite the steps behind the Albert Hall). It is very Gothic in style, with elaborate, brightly coloured decoration, ogee-headed windows where we might expect a rose, and parchment fringes around the soundboard.
The keyboard range, apparently E to g2, is odd, perhaps the bottom note was meant to sound C, and its hand-carved bridge resembling the branch of a tree is surprising, yet many other features are remarkably similar to later instruments. Each key activates a plucking mechanism, which has a tongue that pivots so that on its return, when the key is released, the plectrum passes the string without a second pluck. Each note is furnished with only one string, most likely of brass wire (as some fragments of that kind were found inside), and since it has no provision for dampers, or any trace of soft material that might be remnants of them, we may deduce that it had that distinctive medieval aura of ringing sound, like a psaltery, and consequently ill-defined articulation.
It is difficult to draw any firm conclusions about the state of harpsichord making at that time since it provides us with only a tiny keyhole-sized window into the musical world of late medieval Europe. We cannot tell whether many harpschords were made in this form, or whether its preservation, with very little interference, has been influenced by its very unusual form and decoration.
For a more typical view of early harpsichords our best 
resource might not be surviving instruments but their pictorial representation, in which they are usually played by angel musicians in stained glass windows, or in carved stone embellishments such as roof bosses or corbels. In this example we see what is undoubtedly a horizontal harpsichord in an upper window of the Beauchamp Chapel in St Mary's Church, Warwick. This glass was commissioned from John Prudde of London, and made about 1445. Of slightly later date, probably around 1465, there is a harpsichord carved in wood in Manchester Cathedral, and another in St Wendreda's church, in March, Cambridgeshire. A useful 'Checklist of Fifteenth-century Representations', compiled by Edmund Bowles, can be found in Keyboard Instruments edited by Edwin Ripin, 1971.
A noteworthy feature of most pre-1500 harpsichords is their multiple soundboard roses. The photo above is not sufficiently clear to show them, but there are suggestions of four circular openings beneath the strings, of various sizes, and this is frequently seen in other examples from Sweden, Bohemia, and France. Such multiple roses appear in England in the seventeenth century, as seen in the surviving harpsichord by Charles Haward, perhaps built in 1683, at Hovingham Hall, Yorkshire.
From the early years of the eighteenth century English harpsichords survive in sufficient numbers to make some comments on the prevailing norms. 
Examples by Barton, Hancock, Hitchcock, Smith, and Slade enable us to sample work from a native English tradition whose features include: a preference for walnut as the case material; a pre-shaped pine baseboard around which the sides are assembled; a soundboard with no more than one rose hole (sometimes none); pine or spruce keys faced with ivory and ebony (or reversed) laterally guided by a rack at the distal end; cast brass stops projecting through the fascia board above the keys; and characteristically shaped end blocks at either side of the keyboard. Additionally, they also have battens running vertically at the near end of the cheek and the spine -- functioning also as retainers for the lock board. That's quite a list of features but there is another characteristic uniting them. The preferred keyboard range was based on G not F. A chromatic five-octave compass was standard at an early date – perhaps fairly general by 1715 – so that most spinets and many harpsichords had sixty-one notes, GG to g3, just such a compass as in the harpsichord at which Philip Mercier portrays Handel circa 1728. (The photo shows a copy, made by Michael Cole, for the Handel Museum in London.)
English harpsichord making took a new direction after 1715, with the arrival of Hermann Tabel from the Low Countries. James Shudi Broadwood, writing in 1838, has led everyone astray by stating that Tabel learned his trade in 'the house of the Ruckers in Antwerp'. In fact there is no trace of the Ruckers tradition in Tabel's design, and no indication that he had trained there. (In reality he came from Amsterdam.) Tabel's case was made from oak, veneered with walnut – following neither the English nor the Flemish tradition. His keyboard is of five octaves from FF, [not GG] and his string scaling was exceptionally long – c2 being in excess of 350mm – though we cannot say precisely as the bridge was moved forward, most likely in a restoration at Broadwoods in 1900. They, or Dolmetsch c.1951, changed the key plates so the ebony natural keys we now see are quite possibly not much like the originals. Beneath the soundboard we find the characteristic structures seen in later English harpsichords from Kirckman and Shudi with an oak belly rail from which downward sloping braces take the thrust to the baseboard. The instrument showing here, held by Warwick County Museum, is dated 1721 in Tabel's own hand. It has three sets of strings and four rows of jacks, including a cut-through lute stop played from the upper manual. The nearer eight foot jacks in the main gap are 'dog-legged' so they play from either manual. None of these features suggest an apprenticeship in Antwerp. And, in fact, we now know that Tabel was not from in Antwerp, but Amsterdam.
An inventory drawn up at Cannons in 1720, the grand mansion of Lord Chandos near Edgware, lists a two-manual harpsichord by Tabel, so it is certain that Handel, when employed at Cannons, was among those who played such an instrument. John Wilbrook, formerly Tabel's workman, continued to follow Tabel's example as shown by a two manual harpsichord of 1730, now in Edinburgh. Jacob Kirckman, the most successful London harpsichord maker of all time, was Tabel's foreman in 1738. He and Burkat Shudi, who established competing workshops in London, replicated this design with very few changes during the following decade, but after 1750 they introduced several refinements, changing their keys' balance points, and replacing pine with limewood (Tillia) for their key panels. To improve repetition they added restraining staples in their jacks. Both workshops appear to have decided that a scale of about 340mm for c2 best suited their instruments, strung with German 'steel' wire (i.e.mild steel) in the treble, at a pitch of somewhere near a=425. In common with other London-based furniture makers they switched from walnut to mahogany after 1740.
Pedals to change registrations appeared much earlier than most musicians now imagine. A two-manual Shudi harpsichord in the Royal Collection at Kew (dated 1740) was originally part of a composite instrument -- organ and harpsichord -- equipped with a pedal mechanism to change the registration of the harpsichord and possibly the organ too. (There was a precedent for this in the seventeenth century when Player made instruments with pedals.) Among Kirckman's instruments, and those by other London makers, the 'machine stop' to change registrations was a desirable item for their wealthier clients. When equipped with a 'swell' pedal, players of English harpsichords could create many tone colours and diminuendos at will. Frederick the Great ordered at least three such instruments from Shudi, and Kirckman's harpsichords, taken to Italy, were regarded as phenomenal by musicians in Rome and Naples.
Michael Cole, March 2020