Early Evolution of the Piano
Beginning about 1725, when the noted German organ maker Gottfried Silbermann of Freiberg adopted Cristofori's action, the next major developments took place in Germany. Perhaps the most important contribution was made by Johann Andreas Stein of Augsburg, who is credited with inventing an improved escapement that became the foundation of the “Viennese” piano praised by Wolfgang Amadeus Mozart and favored by most German composers of the late 18th and early 19th centuries. Twelve masters from central Germany migrated to London about 1760 and established the English school that, under John Broadwood and others, turned to the production of pianos of a stronger build, resembling those of our own day. The French manufacturer Sébastien Erard founded the French school in the 1790s, and in 1823 created the double action that is still in general use. By this time artisans in all Western nations were working to perfect the pianoforte. Numerous improvements were and are still being made in design and construction. Germany and the United States have long been distinguished for fine pianos, notably those of the German firm founded by Karl Bechstein and the American firms of Baldwin, Mason & Hamlin, Steinway, and Chickering. The pianos of the Austrian Bösendorfer firm are also highly respected.
The compass of the early piano was, like that of the harpsichord, only four, or at most, five octaves, but it has gradually increased to a compass of more than seven octaves as structural changes allowed for increases in tension amounting to several tons.
Modern Structure
The modern pianoforte has six major parts (in the following discussion, the numbers in parentheses refer to the accompanying diagram (Diagram #1 below) of the structure of a pianoforte): (1) The frame is usually made of iron. At the rear end is attached the string plate, into which the strings are fastened. In the front is the wrest plank, into which the tuning pins are set. Around these is wound the other end of the strings, and by turning these pins the tension of the strings is regulated. (2) The soundboard, a thin piece of fine-grained spruce placed under the strings, reinforces the tone by means of sympathetic vibration. (3) The strings, made of steel wire, increase in length and thickness from the treble to the bass. The higher pitches are each given two or three strings tuned alike. The lower ones are single strings made heavier by being overspun—that is, wound around with a coil of thin copper wire. (4) The action is the entire mechanism required for propelling the hammers against the strings (see Operation of the Action below). The most visible part of the action is the keyboard, a row of keys manipulated by the fingers. The keys corresponding to the natural tones are made of ivory or plastic; those corresponding to the chromatically altered tones, of ebony or plastic. (5) The pedals are levers pressed down by the feet. The damper, or loud pedal, raises all the dampers so that all the strings struck continue to vibrate even after the keys are released. The soft pedal either throws all the hammers nearer to the strings so that the striking distance is diminished by one-half, or shifts the hammers a little to one side so that only a single string instead of the two or three is struck. Some pianos have a third, or sustaining, pedal that does not raise all the dampers, but keeps raised only those already raised by the keys at the moment this pedal is applied. The use of these pedals can produce subtle changes in tone quality. Many upright pianos have been built in which the application of a pedal interposes a strip of felt between the hammers and strings so that only a very faint sound is produced. (6) According to the shape of the case, pianos are classified as grand, square, and upright. The square form (actually rectangular) is no longer built. For use in private homes it has been entirely superseded by the upright, which takes up far less room. Grand pianos are built in various sizes, from the full concert grand, 2.69 m (8 ft 10 in) long, to the parlor or baby grand, less than 1.8 m (6 ft) long.
Upright pianos include the late 19th-century cottage piano, of which the upright grand is merely a larger form. The modern spinet and console pianos are small uprights related to the cottage piano. In the upright pianos the strings run vertically, or diagonally, from the top to the bottom of the instrument. Uprights and small grands are sometimes overstrung; that is, the bass strings are stretched diagonally across the shorter treble strings, thereby gaining extra length and improved tone quality. The combined tension of the strings on a concert grand piano is about 30 tons, on an upright about 14.
Diagram #1
Essentially, when a piano key is pressed down, its tail pivots upward and lifts a lever that throws a hammer against the strings for that key's note. At the same time a damper is raised from these strings, allowing them to vibrate more freely. The following is a much more detailed description of how the action works; the numbers in parentheses refer to the accompanying diagram (Diagram #2 below) of the action of a grand piano.
The piano key (1) is a lever that pivots on a balance pin (2). When the player depresses the key, the tail rises and the capstan screw (3) in the key pushes up the whippen (4), which is hinged. The free end of the whippen rises, taking with it an L-shaped piece called the jack, or escapement lever (5), and the repetition lever (9).
The jack pushes the knuckle, or roller (6), a roll of felt that is fixed to the hammer shank (7); the hammer thus rises. The jack's upward motion is stopped when its protruding end hits the regulating button (8). The hammer flies up away from the jack and strikes the appropriate strings. The repetition lever (9) also rises, but only until the end where the jack passes through it and touches the drop screw (10); this lever stays raised until the key is released.
The hammer falls back, but only partway. It is stopped by the knuckle (6) hitting the raised repetition lever (9). The jack (5) can thus slip back under the partially raised hammer shank and into its original position. At the same time, the backcheck (11) keeps the hammer from rebounding against the strings.
If the key is partly released, the hammer moves free of the backcheck, and the repetition lever stays raised. If the player again depresses the partially released key, the jack (5) can once more push the knuckle (6) and hammer shank (7) upward. (This system allows rapid repetition of notes before the key and hammer have time to return to their original positions. It was an important improvement over early, simpler piano actions.)
Meanwhile, the tail of the key has also pushed up the damper lever (12), which lifts the damper (13) off the strings for that key. When the key is even partially released, the damper falls back onto the strings and silences the note.
When the key is fully released, all parts of the mechanism return to their original positions because of gravity. Unlike grand pianos, upright pianos cannot rely on gravity to cause everything to return to place. In a grand piano the action sits horizontally on the key; in an upright piano the action is adapted so that it sits more or less vertically. Because it cannot completely rely on gravity, it includes various springs and small strips of cloth to pull some of the action parts back into place.
Diagram #2
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