A Popular History of the Art of Music / From the Earliest Times Until the Present

They are three: The vigor of the mental movement in general, its strength upon the imaginative and sentimental side, and the suggestion from the environment in the way of musical instruments of adequate tonal powers.

Every manifestation of musical art has in it these two elements: The fit selection of tones; and, second, the use of them for expressing sentiment and feeling.

they express sentiment.