Mozart used the clavichord now in the Mozarteum at Salzburg in composing his 'Zauberflöte' and other masterpieces, although in playing he leant to the harpsichord style. Beethoven is reported to have said 'among all keyed instruments the clavichord was that on which one could best control tone and expressive interpretation' (Vortrag).
Clavichords made prior to the last century had strings for the lower or natural keys only; the semitones on the upper keys being produced by tangents directed towards the strings of the lower. Thus C♯ was obtained by striking the C string at a shorter length; D♯ in like manner from the D string. We are told that in old instruments three and four keys were often sharers in one string. At last, about the year 1725, Daniel Faber of Crailsheim, gave each semitone its own string, and instruments so made were distinguished as 'bundfrei' from the older 'gebunden.' In the clavichords last made there were two strings to each tangent and note, tuned in unison. An admired effect of the clavichord was a change of intonation, caused by a stronger pressure on the key, which displacing a little the point of contact of the tangent, tightened the vibrating part of the string and made the note very slightly sharper in pitch. [App. p.593 adds "'An admired effect due to change of intonation' is inaccurate. To play out of tune was deprecated by C. P. E. Bach. There is no doubt that clavichord players preserved a very tranquil position of the hand in order to preserve truth of intonation."] Another special grace was that of repeating a note several times in succession without quitting the key, a dynamic effect (German Bebung) which could not be done on the harpsichord, although Beethoven sought to imitate it on the pianoforte with the touch, aided by the double shifting of the soft pedal, which in his day was usual (Sonatas, Op. 106 and 110, Bülow's edition, 1871; pp. 53–108). [Bebung.]
The early history of the clavichord previous to the 15th century, together with that of the chromatic keyboard—a formal division at the very foundation of modern music—rest in profound obscurity. We are still free to regard our keyboard as an invention sprung complete from the brain of some one mediæval musician, or as the result of gradual contrivances due to the increasing requirements of many. The small evidence that can be adduced favours the latter notion.
[App. p.593 "With respect to the introduction of the chromatic keyboard, Hubert van Eyck painted the S. Cecilia panel of the famous Ghent altar-piece in which there is a Positive organ depicted with the chromatic division of the keyboard. He died in 1426, and that was therefore the last year in which this panel could have been painted. It is probable that the Halberstadt organ, built in 1360, had this division. If so, it is the earliest known example."]
However, the keyboard with its familiar division into seven long and five short notes, was not designed to bring within the limits of the octave the theoretical circle of fifths; the short notes or semitones were long used 'per fictam musicam,' and not, like the seven naturals, as practical starting-points for scales. It was not until the epoch of J. S. Bach that the semitones gained equal privileges with the naturals. Again, our chromatic keyboard was not suggested by the 'chromatic' genus of the Greeks, a totally different idea. The problem really solved by it was that of the transposition of the church tones, a series of scales on the natural keys employing each in succession as a starting-point. The first and seventh were consequently nearly an octave apart. Bearing in mind that some of the Latin Hymns embraced a compass of twelve or thirteen notes, it is evident that ordinary voices could not sing them or even those of less extent, without concession in pitch. Arnold Schlick ('Spiegel der Orgelmacher und Organisten,' Mainz, 1511) gives several instances of necessary transposition, which were only possible by the insertion of the semitones between the naturals, as even then it was a law that the interval of an octave should be grasped by the hand, the broader keys of the older organs having been abolished. By this insertion of the semitones they became the willing guides to the cadences; the G♯ alone being doubtful on account of the 'wolf' in tuning. Schlick in his chapter on tuning,—in which he includes the clavichord and clavizymmel (clavicembalo), the symphonia, a smaller keyed instrument, lute, and harp—says that the semitones could not be rightly tuned or brought into concord. But he names all the semitones we now use, and speaks of double semitones having been tried in the organ twelve years before (1499), which failed through the difficulty of playing.
Virdung, a priest at Basel, who published his 'Musica getuscht und ausgezogen' also in 1511, (afterwards translated into Latin as 'Musurgia, seu Praxis-Musicae,' Strasburg, 1536 [App. p.593. adds "the Latin version of Virdung is, as is now well known, by Luscinius, whom many have credited with being the original author."]) is the oldest authority we can specially refer to about the clavichord. The next in order of time, but a hundred years later, is Praetorius ('Syntagma Musicum,' 1614–18). We are told by him that the earliest clavichords had only twenty keys, in genere diatonico, with two black keys (B♭), so there were not more than three semitones in an octave; like the scale attributed to Guido d'Arezzo, the full extent of which would have embraced 21 keys in all [App. p.593 adds"The scale of Guido should include the highest note e, and contain, with the B molle et durum, 22 notes."]—
but Praetorius gives no nearer indication of the compass, and of course none of the pitch. [Hexachord.] But in Virdung's time there were thirty-five keys or more, starting from the F below the bass stave and embracing the complete system of half-tones; and in that of Praetorius at least four octaves, still the usual compass when J. S. Bach wrote the 'Wohltemperirte Clavier.'
By the middle of the century five octaves were attained. Welcker von Gontershausen ('Der Clavierbau,' Frankfort, 1870) endeavours to find a solution to the keyboard problem by starting from the B♭ added to the B♮ of the earliest clavichords, and assumed the gradual introduction to the keyboard of other semitones, until the twelve in the octave were complete, an achievement he attributed to Zarlino (1548). Welcker describes the oldest clavichord he had met with as bearing, in the sound-hole, the date 1520; and through the four octaves of this instrument the notes D♯ and G♯ were wanting! [App. p.593 adds "the statement that there was a clavichord dated 1520, wanting two semitones in the octave, proves to be unfounded. See Welcker's earlier account of it in 'Neu eröffnetes Magazin musikalischen Tonwerkzeuge,' p. 106 (Frankfort, 1855)."] But, after the evidence of Virdung, either Herr Welcker had misread the date or the instrument had been made after an obsolete pattern; yet this solitary instance recorded