Theory and Practice of Piano Construction / With a Detailed, Practical Method for Tuning

by William Braid White

The two types thus described are the most radical exceptions to the common style of metal framing. It is a matter of regret that manufacturers in general have been content to follow so closely in the footsteps of the pioneers, and have not experimented more energetically with a view to effecting other improvements in the accepted methods. The problem of sustaining the necessary tensions would undoubtedly be simplified by the adoption, at least in part, of the ideas of the eminent firms who have already been mentioned.

In order thoroughly to understand the actual advantages and disadvantages of the various styles of framing that have been described, we must consider how great are the tensions that they are compelled to bear. A concert grand pianoforte of a standard American make is so constructed that it bears a total strain, when tuned at concert pitch, of not less than 30 tons. The requirements of increased tone and the weight and bulk of strings tend constantly to augment rather than to decrease these tremendous strains, and at the same time more and more to induce the production of those dissonant partials that have such a maleficent influence upon tone-quality. Obviously, then, if we are to satisfy the popular demand for greater volume, and at the same time to maintain the highest standards of quality, we must seek for some method that will obviate the employment of yet heavier masses of cast iron and at the same time preserve the necessary strength and rigidity. The methods of construction that have been noticed at some length above seem to present manifold advantages over the older styles. Steel has greater tensile strength than iron, and consequently a smaller bulk of it is required. Again, its elasticity is higher and the vibrations impressed upon it traverse its surface with greater facility and in a shorter period of time. Whether, therefore, we prefer the barless or the cupola style of construction, we must recognize the fact that steel is a better material than iron in any form.

Foremost among the requirements of a successful framing system are that it shall sustain its burden with such rigidity that the strings shall stand in tune and the wooden case of the instrument shall not be twisted out of shape. Even if the material be the best possible, a faulty method of securing the metal frame to the case will not only prevent the consummation of these desires, but will tend to weaken the sound-board and hasten its splitting. It is essential, in fact, that the board should be relieved of strain, and great care must therefore be exercised in fitting the framing. The approved method is as follows: The framing is connected with the system of wooden posts that extend below the sound-board and bind together the sides of the case. The latter connection is made by means of long bolts that extend through the bracings of the frame and are sunk into the posts at convenient places. The sound-board is secured to the sides of the case by means of its ribs, which are continued beyond its edges and pocketed into the sides and the posts, and also by being glued to the bottom surface of the case and to the system of posts. Lastly, the frame is connected both with the board and the posts, by a series of heavy screws that pass through the board and into the posts at regular intervals along its outer edges.

This method of securing the frame and sound-board to the case ensures that the former shall be incorporated within the body of the instrument as rigidly as is possible, and that the latter shall have the fullest protection against those twisting strains that the metal frame alone ought to bear.

With such a method as has been described we can find no great fault. It should be noted, however, that in the barless or open scale construction the bolts that were described as passing through the braces into the posts below are omitted, and the whole frame is supported within the case by a series of bolts driven through the turned-up steel flange at equal intervals in its surface.

Having thus considered the forms of framing that are employed by various makers we may turn our attention to the matter of suspending the strings across the frame and over the sound-board. The upward stroke of the hammer of the grand pianoforte tends to drive the string away from its bridge and thus to lessen the energy with which the vibrations imparted to the string are impressed upon the latter. We may note that all makers are agreed in giving to the strings of a grand pianoforte an upward thrust or “bearing” in order that the blow of the hammer may throw the strings against the upper surface of the bearing-bridge instead of away from it. There are two devices that are generally employed for this purpose. They are known as the “agraffe” and the “capo d’astro bar.”

The first of these was the invention of the celebrated Erard of Paris. It consists of a brass stud screwed into the iron framing (or into the wrest-plank where the plate does not extend over the latter), at the beginning of the speaking length of each string or group of strings. This stud is bored with the required number of holes—one for each string in the group. These holes are bored at such an angle that the ends nearest to the tuning-pins are higher than the other ends, while the pins are placed at a higher elevation than the agraffes. In this manner the string is given an upward thrust as it proceeds toward the tuning-pin, and the blows of the hammer force it against the upper surface of the agraffe, which, being solid, conveys the impressed vibrations through the medium of its own surface to the framing.

The “capo d’astro bar” performs the same functions in a slightly different manner. It is practically a continuous “agraffe,” and consists of a metal bar which is cast into the metal frame at the beginning of the speaking length of the strings. It is fitted, according to the best practice, with an under edge of tool steel, and the strings are caused to pass underneath it on their way toward the tuning-pins, which are higher than the bar, as before. The up-bearing is thus imparted to the strings in a manner similar to that which is followed in the case of the agraffes.

As to the advantages of the two systems, it may be said that the “capo d’astro” undoubtedly overcomes those objections to agraffes which are based upon their tendency to pull out from their places. It provides an absolutely rigid resistance, and is therefore stronger and more reliable.

On the other hand, however, the mass of metal employed is considerably greater than in the “agraffe” method, and the resultant influences upon tone-quality are clearly disadvantageous.