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