The fault of the original proposers of the speech theory was that they thought it a complete explanation of the facts of musical expression. Its explanatory value is, however, strictly limited, and supplemental to the more basic considerations adduced; yet it remains a necessary part of the complex theory of the complex fact we are studying. And the acceptance of it as such does not imply a belief in the speech theory of the origin of music. Song did not grow out of impassioned speech, but arose coeval with speech, when men found--perhaps by accident--that they could make with their voices pure and pleasing tones and intervals of tones, and express something of their inner selves in so doing. Yet, as I have suggested, it would be strange if speech did not react upon song--if the first vocal tones were not purified words, and the first intervals an approximation to those of speech. Thus in song, lyric poetry and music arose together as a single art for the expression of feeling, until the development of instrumental music freed the one and the invention of writing freed the other; while speech kept to its different and original purpose--the expression of ideas for practical ends, and produced an aesthetic form of its own only at a later period and under independent influences. The complete understanding of musical expression involves, finally, as was suggested at the beginning of this chapter, the recognition of the analogy that exists between music and the noises produced by nature and human activities. Through the imitation of their rhythm, force, and tempo, some of these can be directly suggested by musicians. Yet this direct suggestion, although employed by the greatest composers, plays a subordinate part in music, and, since it introduces an element of representation of the outer world--_tonmalerei_--is usually felt to involve a departure from the prime purpose of music: the expression of the inner world through the emotional effects of pure sound. In the best program music, therefore, the purpose of the composer is not the mere imitation of nature--which is never art at all, and in music is always recognized as an unsaesthetic _tour de force_ of mere cleverness--but rather the arousal of the feelings caused by nature. And as an aid in the expression of such feelings, imitation, when delicately suggestive rather than blatant, will always play a part.