Melody constitutes, then, a line of tones. If, as we have said, Time is the canvas upon which the musical images are thrown, Melodies are the lines which trace the design or form of these images. This indicates the extreme importance of the melodic idea in music form. Without such "tone-lines" the effect would be similar to that of daubs or masses of color without a drawing, without the evidence of contour and shape.
A good melody, that is, a melody that appeals to the intelligent music lover as tuneful, pleasing, and intelligible, is one in which, first of all, each successive tone and each successive group of tones stands in a rational harmonic relation to the one before it, and even, usually, to several preceding tones or groups. In other words, the tones are not arranged haphazard, but with reference to their harmonious agreement with each other. For a model of good melody, examine the very first sentence in the book of Beethoven's pianoforte sonatas:—
[Illustration: Example 5. Fragment of Beethoven.]
The tones bracketed a, if struck all together, unite and blend in one harmonious body, so complete is the harmonic agreement of each succeeding tone with its fellows; the same is true of the group marked c. The tones bracketed b and d do not admit of being struck simultaneously, it is true, but they are all parts of the same key (F minor), and are closely and smoothly connected; hence their concurrence, though not one of harmony (chord), is one of intimate tone relation and proximity. Further, the whole group marked 2 corresponds in its linear formation, its rising, poising and curling, exactly to the preceding group, marked 1. This, then, is a good melody,—tuneful, interesting, intelligible, striking and absolutely definite.
In the second place, the tones and groups in a good melody are measured with reference to harmony of time-values; that is, their metric condition, and their rhythmic arrangement, corroborate the natural laws already defined:—uniformity of fundamental pulse, uniform recurrence of accent, and sufficient regularity of rhythmic figure to insure a distinct and comprehensible total impression. This also may be verified in the time-values of Ex. 5. Scrutinize also, the melodic and rhythmic conditions of Exs. 1 and 2,—and the examples on later pages,—and endeavor to vindicate their classification as "good" melodies. Ex. 4, though an exposition of irregular rhythm, is none the less excellent on that account; on the contrary, this irregularity, because wisely balanced by sufficient evidence of harmonious and logical agreement, only heightens the beauty and effectiveness of the melody.
Whenever whole bodies of tone are played successively, a number of melody lines are being described,—as many, in fact, as there are tones in each body. For example, in playing a hymn-tune we describe (on the keyboard) the four separate melodies known as the soprano, alto, tenor and bass voices. In a duet, unaccompanied, there are two melodic lines; if accompanied, other melodic lines are added to these. Thus we recognize the same system of associated lines in music as in architecture or drawing. Very rarely indeed does one single unbroken line portray a complete image.
But in music, as in drawing, the lines differ in their degrees of importance and prominence; and, very commonly, one line over-shadows all, or nearly all the rest. This strongest tone-line is therefore apt to be designated, somewhat unfairly, the melody (the "tune" or "air" is more just). But, at all events, this predominating melodic line is the most important factor of the form, the one upon which the definition and recognition of the "form" depend; and it is therefore necessary that the student learn to distinguish it, to acquire the habit of centring his attention upon it,—in reading, listening to, or analyzing music; and, in playing, to give it the emphasis it requires.