In the development of musical scales four stages may be recognized: 1. The stage of primitive music, where there is no more indication of a scale than in the sounds of birds, animals, or of nature. Students of the origin of music may give free rein to their fancy in this period, and the uncertain musical utterances of living primitive peoples may be construed in accordance with almost any prepossession of the hearer. 2. The stage of instruments mechanically capable of furnishing a scale. This stage has been almost entirely overlooked by students and is the special subject of the following paper. 3. The stage of theoretical melodic scales---Greek, Arab, Chinese, Hindu, Mediaeval, etc. All the original treatises concerning these scales imply that a stage of development has been reached far in advance of the second. Thousands of pages have been written on this stage, largely polemical and lacking in insight, for the subject has been a dark one; but Ellis and Hipkins's work of 1885 has thrown a flood of light on it. 4. The stage of the modern harmonic scale and its descendent, the equally tempered scale, which are alike dependent both on a theory and on the possibility of embodying it in instruments. The relation of this scale to the present study will be noticed later. These four stages, of course, overlap even in the same locality; they correspond in a rough way to the recognized four culture stages, namely: the savage, barbarous, civilized, and enlightened.