The full significance of both melody and rhythm depends, however, upon their interrelation, the concrete musical structure, the motive or melody in the complete sense, being an indissoluble unity of both. Now if we take the term will with a broad meaning, Schopenhauer's characterization of melody as an image of the will still remains the truest aesthetic interpretation of it. For, when we hear it, we not only hear, but attend to what we hear; we hear each tone in its relations of harmony or contrast or fulfillment to other tones, freighted with memories of its predecessors and carrying with it expectations, which the following tones fulfill or deny. The melody begins, let us suppose, with the tonic note. This note then becomes for us a plan or purpose; for as it goes, it leaves in the mind a memory of itself, no mere pale sensation--no image ever is--but a motor set, an expectation and desire to hear the note again. If the next note is harmonically related, this purpose is partially fulfilled and we get the satisfaction of a partial success. If, however, the tone does not belong to the tonic chord, but, let us suppose, to the subdominant, it comes as a hindrance, an obstacle, or perhaps as a new and rival purpose springing up in the course of the fulfillment of the old,--a purpose which can be satisfied only through the other tones of its chord. Hence the tension of conflicting expectations and the excitement as now the one and now the other is fulfilled in the succeeding notes. Yet, since all other harmonies are subordinated to the tonic harmony, and even through their very opposition increase our desire for it, they must give way to the fundamental purpose with which we started; and when the tonic does eventually triumph, it fulfills not only itself, but all lesser desires of the melody; in it we find what we have been seeking, we arrive where we set out to go. And in this success we not only obtain what we first wanted, but more--an experience enriched by every conflict, and harmonious ultimately through the inner adjustment and resolution of its elements; for in hearing the final note we hear the memories of all previous tones, also. When the departures from the keynote are many and distant and sudden, and the melody wanders into the bypaths of foreign harmonies, moving along broken and zigzag lines, it expresses an exciting, a dangerous and difficult adventure; when, however, the departures are gradual and confined for the most part within the limits of a single harmony, moving in a smooth and curving path, it expresses a life that is secure and happy, tending to repose as the line approaches the horizontal, and as repetitions of the same note predominate.