Piano-fortes are at present of three kinds, 1st, small or square ; 2d, grand ; these two may be conceived as repre senting the spinet and harpsichord of former times; and, 3d, the cabinet piano-forte, a medium between the two first. The square and cabinet piano-fortes have two strings in unison, and the grand piano-forte has three unisons to each finger-key. One end of the string is hung on a fixed pin, and the other is wound round a tuning pin, which turns in a wooden block. The length of the sounding part of the string is determined by two bridges, over which it passes, one on the block in which the tuning pins are in serted, and the other is placed on the sound-board. This last bridge is now divided into two, one for the steel-strings, that is, from the top of the scale down to A on the first space of the bass, and the other for the brass strings. The reason of this division is, that the steel strings require a greater degree of tension than the brass, and the divi sion of the bridge favours both the tone and the keeping in tune.
The original scale of the piano-forte was from FF (oc tave below that immediately under the staff of the bass) up to f in alt. comprising five octaves; and this has been gradually extended. The first addition was of half an octave upwards to c in altissimo. Then the scale was car ried down to CCC ; that is, half an octave lower than FF. And latterly, extra additional keys in the treble have car ried it up to fin altissimo, comprehending six octaves and a half. These gradual extensions have improved the tone of the instrument both in quantity and quality, though the extra notes below are generally in themselves so indistinct, as to deserve the name of noise rather than that of musi cal notes.
While these extensions of the scale have been taking place, the weight of the strings has been continually in creasing. The sizes at present made arc as follows : From pitch C to the top, steel wire No. 10 ; from pitch C to middle C (the octave below) No. I ; and from middle C down to D, 3d line of the bass No. 12. and thence to No. 13. A is a brass string, No. 12.; and the sizes in crease very fast in going downwards. The largest size in the grand piano-forte is No. 17. Formerly the smallest steel strings were small No. 9. and the largest No. I I. ; the largest brass was No. 14. about half the present sizes. In the square and cabinet piano-fortes a sufficient length of string cannot be obtained. Strings covered with small brass or copper wire are used, in order to obtain the depth of tone from about half an octave above FF down to the bottom of the scale ; and, in the grand piano-forte, from FF downward. The quality of these covered strings has been greatly improved by making the covering wire smaller, but laid close together like that of the bass string of the violin.
Few people are aware of the immense strain which the framing of the piano-forte has to sustain. In order to be
able to speak with some precision on this subject, the wri ter of this article made, or rather witnessed, the following experiment : A wire of the size of that used for pitch C, was hung at one end on a pin fixed in a board, and laid over two moveable bridges, which were placed so as to make the sounding part of the string the same length with that in the instrument. Weights were then appended, till the string became unison with the tuning fork ; the weight required was found to be 501b. The same experiment be ing made with middle C, the weight was found to be 571bs. and with A the weight was 81 lb. The brass strings were found to require a weight of 401b. Now, taking the ave rage of these four 57, as the average of the whole, which cannot be very wide of the truth, the strain on a grand piano-forte with unisons and 78 finger-keys, is 13,3381b. that is, nearly six tons.
To sustain so great a strain, the small piano-forte is built of a strong square frame, with a very thick bottom, upwards of three inches of white Swedish pine. The grand and cabinet piano-fortes, instead of a solid bottom, are built with a frame-work of strong beams, four inches in depth by two in breadth, running the length way of the instrument, and tied with cross beams at several distances in the length to prevent them bending. This framing lies immediately below the sound-board.
Notwithstanding every precaution, so great is the strain, and so much are the wood framing and strings affected by the changes of the weather in opposite directions, that the grand piano-forte especially, stands very ill in tune. In order to remedy this defect, chiefly in instruments sent abroad, Mr. Stodart, of London, conceived the idea of substituting metal tubes instead of the wood framing, which, he imagined, being similarly affected by changes of temperature with the strings, would tend to keep the instrument better in tune ; and he found that he had not only obtained his end, but a very great unlooked for im provement in the power and quality of the instrument. In order to adapt his tubes more nicely to the end, he makes them of iron over the steel strings, and of brass over the brass strings. They are placed over the strings instead of below the sound-board, in order to allow the vibrations of the latter to act on a greater body of air below it. But in whatever way the effect is produced, it is unquestiona ble that he has obtained a very superior tone, both in point of quality and quantity. The lowest notes in the extra finger-keys below, instead of a chaos of sound, are as clear and distinct as any part of the scale ; and in a concert room, the instrument tells in a style to which the piano forte formerly had no pretensions. At the same time the advantage in point of keeping in tune is very remarkable.