I
The striking difference between the pianoforte music of the nineteenth century and that of the eighteenth is, of course, not an accident. That of the eighteenth is in most cases not properly piano music at all, since it was composed specifically for the clavichord or harpsichord, which have little beyond the familiar keyboard in common with the modern pianoforte. Both classes of instruments were known and in use throughout the greater part of the eighteenth century, and the date 1800 may be taken as that at which the pianoforte displaced its rivals. Much of the old harpsichord music is played to-day on the piano (as, for instance, Bach’s preludes and fugues), but the structure of the music is very different, and the effect on the piano gives no idea of the effect as originally intended.
The most superficial glance shows eloquently the difference between the two sorts of keyboard music. That of the nineteenth century differs from its predecessor in its emphasis on long sustained ‘singing’ melody, in its greater range, in its reliance on special tone qualities, in being (to a great extent) melodic instead of polyphonic, in wide skips and separation of notes, and, above all, in its use of sustained chords. Leaving aside the specific tendencies of the romantic period, all these differences can be explained by the difference in the instruments for which the two sorts of music were written.
The clavichord was a very simple instrument of keys and strings. The length of the vibrating string (which determines its pitch) was set, at the stroke which set it in vibration, by a metal ‘tangent’ on the end of the key lever, being at once the hammer and the fret of the string. The stroke was slight, the tone was extremely soft. The vibration continued only a few seconds and was so slight that anything like the ‘singing tone’ of the pianoforte was impossible. But within the duration of a single note the player, by a rapid upward and downward movement of the wrist which varied the pressure on the key, could produce a wavering tone similar to the vibrato of the human voice and the violin, which gave a faint but live warmth to the tone, unhappily wholly lacking in the tone of the pianoforte. It was doubtless this peculiar ‘live’ expressiveness which made the instrument a favorite of the great Bach, and which, moreover, justifies the player in making the utmost possible variety of tone in playing Bach’s clavier works on the modern instrument. The sound of the instrument was something like that of an æolian harp, and was therefore quite unsuited to the concert hall. But it was of a sympathetic quality that made it a favorite for small rooms, and much loved by composers for their private musings.
The harpsichord was the concert piano, so to speak, of the time. Its strings were plucked by means of a short quill, and a damper automatically deadened the tone an instant afterwards. The instrument was therefore quite incapable of sustained melody, or of gradations of volume, except with the use of stops, which on the best instruments could bring new sets of strings into play. Its tone was sharp and mechanical, not very unlike that of a mandolin.
Now what the modern pianoforte possesses (apart from its greater range and resonance) is chiefly ability to control the power of the tone by force or lightness of touch, and to sustain individual notes, by means of holding down the key, or all of them together through the use of the sustaining pedal. Theoretically, the clavichord could both control power and sustain notes, but the tone was so slight that these virtues were of little practical use. The ground principle of the pianoforte is its rebounding hammer, which strikes the string with any desired power and immediately rebounds so as to permit it to continue vibrating. Each string is provided with its damper, which is held away from it as long as the key is pressed down. The sustaining or damper pedal removes all the dampers from the strings, so that any notes which are struck will continue vibrating. The one thing which the piano cannot do is to control the tone after it is struck. By great care in the use of materials piano makers have been able to produce a tone which continues vibrating with great purity and persistence, but this inevitably dies out as the vibrations become diminished in amplitude. The ‘legato’ of the pianoforte is only a second best, and is rather an aural illusion than a fact. Any increasing of the tone, as with the violin, is quite impossible. Any true sustaining of the tone is equally impossible, but, by skillful writing and playing, the illusion of a legato tone can be well maintained and a far greater beauty and variety of effect can be reached than one might think possible from a mechanical examination of the instrument.
Before 1770 (the date of Beethoven’s birth) clavier music existed only for the clavichord and the harpsichord, though it could also be played on the pianoforte. Beethoven grew up with the maturing pianoforte. By the time he had reached his artistic maturity (in 1800) it had driven its rivals from the field. Up to 1792 all Beethoven’s compositions were equally adapted to the piano and the harpsichord. Up to 1803 they were published for pianoforte or harpsichord, though it is probable that in the preceding decade he had written most of his clavier music with the pianoforte in mind.
The earliest pianoforte (made in the first two decades of the eighteenth century) had a compass of four and a half octaves, a little more than that of the ordinary clavichord. The pianoforte of Mozart’s time had five octaves, and Clementi added half an octave in 1793. By 1811 six and a half octaves had been reached, and in 1836 (about the time of the publication of Liszt’s first compositions, barring the youthful Études) there were seven, or seven and one-third, which have remained the standard ever since. During all this time piano makers had been endeavoring to increase the rigidity of the piano frame. This was partly to take care of the greater size due to the adding of bass strings, but chiefly to permit of greater tension. The quality and persistency of the vibration depends to a great extent on the tension of the strings. Other things being equal, the excellence of the tone increases (up to a certain limit) with the tension. This led gradually to the introduction of iron supports, and later to a solid cast iron or steel frame, though up to 1820 only wood was used in the body of the pianoforte, until the tension became so great and the pitch so high (for the sake of tonal brilliancy) that the wooden frame proved incapable of sustaining the strain. The average tension on each string is, in the modern piano, some one hundred and seventy-five pounds, and was up to recent times much higher. The present Steinway concert grand suffers a strain of more than twenty tons, and, under the higher pitch of former years, had to stand thirty. The weight of the instrument itself is half a ton.
These improvements have made the piano second only to the orchestra for all around usefulness and expressiveness. The size of the instrument and the high tension of the strings made its tone sufficient for the largest concert hall, and permitted a keyboard range almost double that of the harpsichord. The individual dampers responsive to the pressure of the key made a quasi-legato and true melody playing possible. The rebounding hammer directly controlled by the key made possible all varieties of soft and loud tone. And the sustaining or damper, incorrectly called the loud pedal, made possible the sustaining of chords in great richness. The usefulness of this last device is still not half stated in saying that chords can be sustained; for, when all the strings are left open, there occurs a sympathetic vibration in the strings which are not struck by the hammers but are in tune with the overtones of the strings that are struck. This fact increases to an astonishing extent the resonance and sonority of any chords sounded with the help of the sustaining pedal. It makes the instrument almost orchestral in quality, opening to it an amazing range and variety of effect which Chopin, Liszt, and many piano writers after them, used with supreme and magical skill. The soft pedal opens another range of effects. On the grand piano it shifts the hammers so that they hit but one of the three strings proper to each note in the middle and upper registers. Hence the direction una corda, written in the pianoforte works of all great masters, including Beethoven.
The piano thus became an ideal sounding board for the romantic movement. It was capable of luscious expressive melody. It could obtain effects of great delicacy and intimate character. It could be loud, astonishing and orchestral. Its tone was in itself a thing of sensuous beauty. Its freedom in harmony was no less than its freedom in melody, and enharmonic changes, beloved of all the romanticists, became easy. It allowed the greatest liberty in the disposition of notes, and harmonic accompaniment, with broken chords and arpeggios, could take on an absolute beauty of its own. This sufficiently explains the complete change in the method of writing clavier music in the nineteenth century. One example of the way in which Mozart and Chopin obtained harmonic sonority in accompaniments will show how far-reaching the change was.
Mozart: Sonata in F major
Chopin: Nocturne Op. 27, No. 2
By the use of the damper pedal the Chopin formula gives the effect of a sustained chord. On the harpsichord it would have sounded like a few notes too widely scattered to be united in sonority.
With such an instrument every style of music became possible. Liszt asserted that he could reproduce any orchestral effect on it, and many of the best orchestral works of his time became generally known first through his pianoforte arrangements of them. Equally possible were the simple song-like melodies of some of Chopin’s preludes, or the whimsical genre pieces of Schumann. As a consequence the wonderful piano literature of the nineteenth century is equal to any music in range, power, and emotional expressiveness.