The French horn has the lungs of the performer for a motor, the lips for a vibrator, and the gradually enlarging tube, terminating in the flaring bell, for a resonator.

In the pianoforte the hammer-stroke, the strings, and the sounding-board perform the corresponding offices.

Though improvements in other parts of the piano have done much to increase the volume of the tone, yet in the radical change of form, size, and other physical qualities of the sounding-board consists the evolution of the modern pianoforte from the primitive clavichord.
In all these instruments the quality and power of the tone depend upon the presence of these three elements,--the perfection of their construction, their proper relation as to size and position, and the perfect adaptation of each part.

A split sounding-board spoils the pianoforte, the indented bell destroys the sweet tone of the French horn, and a cracked fiddle is the synonym for pandemonium itself.
The quality and power of resonance is well illustrated by a tuning-fork, which, if set in vibration, can, unaided, scarcely be heard by the person holding it.

But if rested on a table, or a plate of glass, or, better still, on the bridge of a violin, its tones may be distinctly heard throughout a large hall.
The vibrating violin string when detached from the body of this instrument, although attuned to pitch, gives absolutely no musical sound; the lips of the player placed on the mouthpiece detached from the tube and bell of the brass instrument produce only a splutter; and a pianoforte without a sounding-board is nil.