The oval spinet is a type of harpsichord invented in the late 17th century by Bartolomeo Cristofori, the Italian instrument maker who later achieved fame for inventing the piano. The oval spinet was unusual for its shape, the arrangement of its strings, and for its mechanism for changing registration.
The two oval spinets built by Cristofori survive today. One, built in 1690, is kept in the Museo degli strumenti musicali, part of the Galleria del Accademia in Florence. The other, from 1693, is in the Museum für Musikinstrumente of the University of Leipzig. Cristofori built the two oval spinets for the Medici family of Florence. His patron, Prince Ferdinando, needed a compact instrument with multiple string choirs for a small theatre.
Design
String layout In the oval spinet, the strings were placed parallel to the keyboard, the same arrangement as in a virginals. This can be seen in the following schematic false-color diagram of the 1690 oval spinet, showing the outline, keyboard, bridges, and string arrangement. The diagram and those that follow are colorizations of an original by Tony Chinnery.
Unlike in a virginals, the longest strings in an oval spinet are placed in the middle. The strings are arranged so the pair of strings that sounded the lowest note (C) are precisely in the middle, the next lowest pair (C#) is just behind the lowest pair, the third lowest pair (D) just in front of the lowest pair, and so on. Because of the alternating pattern, the highest two notes are the frontmost and hindmost string pairs, thus the farthest apart. By placing the strings in this way, the oval spinet has a (very roughly) oval shape; hence its name.
Arrangement of jacks and keyboard As in all harpsichords, the strings in the oval spinet are plucked by plectra suspended in jacks, thin vertical strips of wood. Each jack rises from the far end of its key, passes through a guiding register in the soundboard, and terminates adjacent to its assigned string, close enough for the bit of quill held by the jack - the plectrum - to pluck the string. In the diagram above, keys labeled with aqua dots lift the jacks that pass through the slots shown in aqua, and keys labeled in maroon control jacks passing through slots labeled with the same color. This arrangement is feasible because the keys are of alternating lengths. These are shown in the following diagram of the keyboard, which rests in the lower part of the case, mostly obscured by the soundboard. The keys are color-coded in the same way as in the first diagram. The same color-coding appears at the far end of each key, schematically indicating the portion of the key that engages the lower end of the jacks.
As can be seen, underneath the keys are two balance rails, one for the keys that play the front row of jacks, the other for the keys that play the rear row.
Advantages of the design Cristofori's design permits a structurally very stable instrument. 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). For reasons having to do with the string lengths, the curve of the bentside must be concave, making it naturally weak. In contrast, in an oval spinet the strings pull at either end on a convex arch, an inherently very strong configuration. Maintaining the integrity of the case was evidently important to Cristofori. 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. This protected the soundboard from possible warping should the outer bentside be pulled out of position. A second advantage of Cristofori's oval spinet design is that it allows for a more compact instrument. 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. The spinet harpsichord, which saves space by arranging the strings in slanted pairs, is still much longer than it is wide. Virginals, which enclose their triangle of strings in a rectangular box, have a great deal of unused space. In comparison with these designs, Cristofori's quasi-oval layout stands out for its compactness and efficiency.
Changing registration Cristofori's oval spinets have two choirs of strings, each at 8-foot (normal) pitch. In the pairs of strings seen in the diagram above, each pair consists of one string from each choir. The purpose of having two choirs was evidently twofold. First, when both strings are played at once, a louder sound is obtained. Second, the two choirs of strings have different timbres, so contrasting tone qualities can be obtained by selecting just one choir. The contrasting timbres result from two factors. Owing to the slant of the bridges, in each pair the string closer to the outer edge of the case is shorter. Moreover, it is plucked relatively closer to the bridge, which emphasizes higher harmonics. 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.
In playing the oval spinet, the player selects a registration; that is, the particular choirs (longer strings, shorter strings, or both together) that will be sounded when a key is depressed. Cristofori accomplished this end with an ingenious mechanical arrangement. For the keys that play the near row of jacks (closer to the player), the mechanism works like this. The portion of the key that engages the lower end of the jack is U-shaped, with each prong of the U ending in a wide, flat upper surface. (This U-shaped part is shown in blue in the false-color diagrams below.) The entire keyboard mechanism can be slightly shifted toward or away from the player, using knobs at the sides of the keyboard. Depending on the location of the keyboard, the jacks will be aligned in different ways against the U, resulting in different strings being played. The three possibilities are shown in the diagrams below, which depict sounding jacks in green, silent ones in red. When the keyboard is fully extracted (pulled toward the player), the jack closer to the player is aligned with the slot of the U, so that only the string plucked by the jack farther than the player (the longer string) will sound.
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