Oval spinet
This can be seen in the following schematic false-color diagram of the 1690 oval spinet, showing the outline, keyboard, bridges, and string arrangement.
As in all harpsichords, the strings in the oval spinet are plucked by plectra suspended in jacks, thin vertical strips of wood.
In a normal harpsichord, the far ends of the strings pull on the bentside (the long, curved, slanting side of the case, at the player's right).
In contrast, in an oval spinet the strings pull at either end on a convex arch, an inherently very strong configuration.
Later on, in his (standardly-shaped) pianos and harpsichords, he employed two separate bent sides, one to support the soundboard and the other to bear the tension of the strings.
When the strings of a keyboard instrument are laid out in the simplest way (ascending in pitch from left to right, as in full-size harpsichords), the resulting triangular shape is space-consuming and inefficient.
Cristofori enhanced the difference in plucking points by placing the plectra on opposite sides of the jack in the two choirs, as seen in the detail figure below.
The other surviving oval spinet by Cristofori, from 1693, has no split keys, but implements the same range (four octaves, C to c''') using a normal keyboard.
[2] Cristofori first drew a line exactly 13 Florentine soldi long (a soldo was, at the time, 27.56 mm) to serve as the base of the arch.
Cristofori's patron was Prince Ferdinando, the son of Grand Duke Cosimo III and heir to the Tuscan throne.
Prince Ferdinando, a great opera enthusiast, organized many operatic productions at the Medici villa at Pratolino.
According to William Holmes (references below), the prince often participated as the continuo player, seated at a harpsichord among the orchestral musicians.
The next Medici instrument inventory, evidently made by Cristofori himself, dates from 1716, three years after Prince Ferdinando's death.
[3] Musical instrument scholar Stewart Pollens called the oval spinet "a tour de force of mechanical design, fully the product of Cristofori's inventive character.
As noted above, the impetus for the oval spinet may have been Prince Ferdinando's wish for a compact multi-choired harpsichord suited to the orchestra pit.
It may be that Ferdinando thought the spinettone a better solution to the problem of making a small but audible continuo instrument than the oval spinet.
While Cristofori's spinettoni were constantly loaned out from the Medici collection for use, this is not so for the oval spinets, which according to Montanari "remained in the same places, gradually deteriorating."
Given that the oval spinet failed to achieve popularity at the Medici court, it is unlikely it would have been adopted in society at large, given the expense of building it and the conservatism of the instrument-makers' guilds of the time.
The other surviving oval spinet was discovered only in the year 2000, having sat unnoticed in storage for a great period of time in the vast collections of Stefano Bardini, an antique dealer around the turn of the 20th century.
The long period when the instrument sat unnoticed was due in part to delays in the transfer of the Bardini collection from his heirs to public ownership.
The equipment and techniques employed included a frame-mounted laser pointer device (to establish dimensions without any need to touch the instrument), X-rays (to detect case-internal parts), optical microscopy (identification of wood species), electron microscopy (for wire and pin composition), and infrared spectrophotometry (to identify glue).
To preserve the instrument's historical value, Italian authorities placed it on display unchanged in the Museo degli Strumenti Musicali in the Galleria del Accademia.
To give a sense of what the instrument was like when it was new, they commissioned harpsichord builders Tony Chinnery and Kerstin Schwarz to build a modern copy (pictured above), which the museum displays alongside the original.
