January 13, 2021
These figures were first observed by Dr. Thomas Young, who obtained them by allowing a ray of sunlight to strike a wire on the pianoforte.
Some of the curves given under such circumstances are shown in the figure below. We shall see that the quality of tone depends on the form of the sonorous wave. It is manifest, then, that even when the tension, length, and material of a vibrating string remain the same, the tones elicited from it may vary in quality, just as its vibratory motions may vary. This is strikingly illustrated by the tones obtained from a violin by a beginner and by a virtuoso. Although the string emitting a given note may remain unchanged as to tension, length, and material, the sound produced is in the one case peculiarly rasping and scratching in character, while in the other case it is remarkable for great purity, steadiness, and volume. The bowing, and the motions of the string consequent on the bowing, are the sole causes of the great difference in the quality of the tones in question.
Passage from Sound and music
By John Augustine Zahm, 1892