The idea so largely accepted that music is an unfathomable mystery, like all half truths has wrought much mischief, and has greatly retarded musical progress in social life. Behind the Divine Art, as behind Religion, lies the inscrutable mystery of Life, and in both there is a Holy of Holies only the consecrated may enter. Before the portals of this are reached there is a broad, fertile field for intellectual activity that all may work to advantage, preparing the way to the inner sanctuary. The musician is continually confronted with fresh evidence of the popular ignorance, even among students of music, in regard to the outward form and inner grace of what is conceded to be the most popular of all arts. In a roomful of professed music lovers a definition of counterpoint was recently called for, and no one present could give an intelligent answer. This led to a discussion of musical questions which resulted in the disclosure that not one of the company could define melody, harmony or rhythm, or had the slightest conception of the meaning of the simplest component parts of the art in whose service they were making plentiful sacrifices. Some knowledge of these things is absolutely imperative, not alone to the student, but to one as well who would listen intelligently to music. Sound and motion constitute the essence of music. Its raw materials are an infinitely rich mass of musical sounds that bear within themselves the possibility of being molded into form. By the musical builders of the past they have been carefully considered, mathematically calculated, and have finally resolved themselves into a recognized scale, composed of tones and half tones. These are the composer's plastic resources. He shapes them precisely as the sculptor fashions the pliable clay with which he strives to bring his ideal to realization. All sounds are the result of atmospheric vibrations affecting the ear. Musical sound, or tone, is produced by regular vibrations, and differs from mere noise whose vibrations are irregular and confused. The pitch of a musical tone rises in proportion with the rapidity of the vibrations that produce it. Tones may be perceived by the human ear ranging from about sixteen vibrations in a second to nearly forty thousand, more than eleven octaves. Only about seven octaves are used in music. The science of acoustics is full of interesting facts of this kind, and is of profound value to any one who would gain an insight into the structure of music. It is unfortunately much neglected.