very important factor in pianoforte tone is the hammer, both in its covering and in its striking place against the string. Helmholtz shows that a soft hammer causes softer or rounder tone because the greater continuity of contact of the soft material damps the very high upper partials, while the less continuity of contact of a hard-surfaced hammer allows small section's of the string to sound on. Strength of blow causes loudness by increasing the amplitude or greater vibrating excursion of the string, while it also expends more energy and increases the number of upper partials in the tone. Weakness of blow is, of course, of reverse influence. The striking-place, or point of contact of hammer and string, affects the tone variously. Experience teaches that it should be upon a nodal point, although many pianoforte makers neglect an accurate adjustment of the striking line, to the detriment of purity of tone. If the string could be struck exactly at the half of its length between the bridges, a kind of clarinet tone of great beauty would be obtained. On the other hand, by striking very near the wrestplank bridge, and thus favouring the very high partials at the expense of the lower ones, an approximation to the oboe tone would be gained. The so-called 'Lute' stop, in the harpsichord, is a practical illustration of this change of quality. The best fundamental tone in combination with the best sounding partials is obtained at the eighth of the string; at the ninth the tone hardens by diminution of the power of the prime, which is proved by the hammer requiring more 'toning' or softening. The high upper partials continue to come into greater prominence as we ascend to the tenth and higher, for which reason, to get brighter trebles, pianoforte makers have adopted the device of bringing the striking-place inwards as they ascend, with a loss of equality of tone. In the old keyboard instruments which preceded the pianoforte, and indeed in the early pianofortes, no attention was paid to accuracy of striking-place. In Harpsichords and spinets the strings were usually touched somewhere between the half and the tenth of the length; but the small diameter of the strings favoured the due formation of agreeable upper partials.[1]
The framing and weight of stringing have much to do with the bars attached to the under side of the belly or soundboard of a pianoforte. These bars cross the direction of the grain of the Spruce Fir of which the belly is made, and promote the elasticity of this most important tone reinforcer. Without the Resonance table the strings would offer scarcely any sound, and without the elasticity gained by the bars their high upper partials would be imperfectly reflected, or immediately lost. The hard wood bridge carries the complete pulsations of the strings to the soundboard by alternating greater and less pressures. On the whole no other musical instrument is capable of the infinite variety of the tone qualities of the pianoforte, as various as the wonderfully nervous touch of the ends of the fingers of the player, which differs in every individual so that no two persons produce quite the same tone from the pianoforte unless they may be said to agree in the bad tone obtained by inelastic thumping.
We can compare, although remotely, the violin with the pianoforte in some of the fundamental principles of tone-production, but in many respects these instruments are very different. For instance, in the tone-production, the string clings to the bow until it is suddenly detached, when it rebounds and is caught by the bow again. Thus a peculiar vibrational form ensues, in which, according to Helmholtz, the prime or fundamental tone is stronger than in the pianoforte, while the first upper partials are comparatively weak. The sixth to the tenth are much stronger, which gives the bowed instruments their cutting character—the 'scolding violins,' as old Thomas Mace called them when they were beginning to supersede the viols and lutes. Any scratching of the bow is immediately shown by sudden jumps or displacements of the compound figure of vibration. The form of this figure is however tolerably independent of the place of bowing, usually at about one-tenth of the length of the string. The quality becomes somewhat duller as we approach the fingerboard, and brighter as we approach the bridge, at least for forte passages. We have resemblances to the pianoforte in the pressure of stopping in the violin by the finger, in the pianoforte by a firm wrestplank bearing; by this power the production and continuity of the upper partials is assisted and maintained. The 'bass bar' in the violin answers to the more complex barring of the piano, by screwing the belly up to the required pitch of elasticity for the reinforcement of the upper partials. Lastly, the bowing has some analogy to the touch of the pianoforte player; in that quality of individuality which extinguishes or subordinates the mechanical in performance.
Recent researches have proved that the orchestral division of wood and brass in wind instruments is nominal, or nearly nominal, only. The material affects the tone of those instruments by the rigidity or elasticity which it offers for enclosing columns of air. The cause of the difference of the quality of tone is the shape of the air column as it approximates to a cylindrical or conical form, and is wide or narrow for the production of the proper tones; the upper partials as determining the quality, and in combinations as harmonics. The production of the tone—whether by double reed (as in the oboe), by single reed (as in the clarinet), or by embouchure (as in the flute); the hypothetical air reed in flue organ pipes, and the action of the lips as vibrating membranes in the cupped mouthpieces of horns, trumpets, trombones, etc.—has its place in the determination of quality; so much so, that to preserve the colour of tone in the orchestra, clarinets and oboes have not been improved, as the flute
- ↑ The effect of the striking is due, generally, to the intensity of motion of the simple vibrations, and the corresponding increase or decrease of the partials, at the point of excitement by the hammer, thus affecting the composition of the musical tone. Helmholtz (Ellis) p. 123.
