trustworthy practical information.

In a unique specimen with two keyboards dating from the 16th or 17th
century, which is in the collection of Baron Alexandre Kraus,[3] what
appear to be vibrating strings stretched over a soundboard perpendicular
to the keyboard are in reality the wires forming part of the mechanism
of the action. The arrangement of this mechanism is the distinctive
feature of the clavicytherium, for the wires, unlike the strings of the
upright spinet, increase in length from _left to right_, so that the
upright harp-shaped back has its higher side over the treble of the
keyboard instead of over the bass. The vibrating strings of the
clavicytherium in the Kraus Museum are stretched horizontally over two
kinds of psalteries fixed one over the other. The first, serving for the
lower register, is of the well-known trapezoid shape and lies over the
keyboards; it has 30 wire strings in pairs of unisons corresponding to
the 15 lowest keys. The second psaltery resembles the kanoun of the
Arabs, and has 36 strings in courses of 3 unisons corresponding to the
next 12 keys, and 88 very thin strings in courses of 4, completing the
49 keys; the compass thus has a range of four octaves from C to C. The
quills of the jacks belonging to the two keyboards are of different
length and thickness. The jacks, which work as in the spinet, are
attached to the perpendicular wires, disposed in two parallel rows, one
for each keyboard.

There is a very fine specimen of the so-called clavicytherium (upright
spinet) in the Donaldson museum of the Royal College of Music, London,
acquired from the Correr collection at Venice in 1885.[4] The instrument
is undated, but A.J. Hipkins[5] placed it early in the 16th or even at
the end of the 15th century. There is German writing on the inside of
the back, referring to some agreement at Ulm. The case is of pine-wood,
and the natural keys of box-wood. The jacks have the early steel
springs, and in 1885 traces were found in the instrument of original
brass plectra, all of which point to a very early date.

A learned Italian, Nicolo Vicentino,[6] living in the 16th century,
describes an _archicembalo_ of his own invention, at which the performer
had to stand, having four rows of keys designed to obtain a complete
mesotonic pure third tuning. This was an attempt to reintroduce the
ancient Greek musical system. This instrument was probably an upright
harpsichord or clavicembalo.

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