16. What are the two vital requisites upon which the enjoyment of an art creation depends?
17. What purpose does Unity serve?
18. What purpose does Variety serve?
19. What is the great problem of the art-creator?
20. Define the conditions that confirm the principle of unity in music.
21. Define the evidences of variety in music.
CHAPTER II. FUNDAMENTAL DETAILS.
TIME.—Time is the same thing in music that it is everywhere else in nature. It is what passes while a piece of music is being played, sung, or read. It is like the area of the surface upon which the musical structure is to be erected, and which is measured or divided into so many units for this, so many for that, so many for the other portion of the musical Form. Time is that quantity which admits of the necessary reduction to units (like the feet and inches of a yardstick), whereby a System of Measurement is established that shall determine the various lengths of the tones, define their rhythmic conditions, and govern the co-operation of several melodies sung or played together. Time is the canvas upon which the musical images are drawn—in melodic lines.
TEMPO.—This refers to the degree of motion. The musical picture is not constant, but panoramic; we never hear a piece of music all at once, but as a panorama of successive sounds. Tempo refers to the rate of speed with which the scroll passes before our minds. Thus we speak of rapid tempo (allegro, and the like), or slow tempo (adagio), and so forth.