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_.