During the modern evolution of musical composition, many new forms were devised bearing descriptive names. Some of these forms by their distinctive tempo, dynamics, or title conditioned the informed listener to a mental attitude consistent with the intention of the composer. Some selections by the very nature of their execution cause stimulation or assist repose. Superficially it might seem, therefore, that the controlled administration of music could evoke desired moods in listeners at will, and some practitioners declared that music is a specific treatment for mental disease. It is undoubtedly possible to influence the mood of healthy, trained musicians by the use of selected compositions but to assume that all listeners will react in similar fashion, or that the moods of the mentally deranged can be changed at will by prescribed music, is to ignore the nature of mental disease and the scientific finding of psychologists. Music is many things, but physically it consists of sounds or notes which have pitch, intensity, timbre and duration. These notes are combined in patterns which have rhythm, tempo, melody and harmony and these in turn are related to key, mode and form. Each of these elements has been the subject of philosophic interpretation, and more recently of psychologic investigations. Although the effect of music on the human mind depends upon the reaction to the entire composition, it is important to review the existing data in order to understand more fully the effects of music, in spite of the difficulties; for as Ortman[71] has said “the problem of analyzing and classifying responses of music into types is at the same time intensely interesting and notoriously difficult. The history of the problem is rich in unco-ordinated data and poor in clear-cut conclusion.” II ELEMENTS OF MUSIC _Pitch._ Heinlein[45] found that the same chords which called forth a happy and bright feeling when played in high pitch were characterized as gloomy or melancholy when played in low pitch. The voice of youth and laughter is higher pitched than the grumbling of old age and may be a conditioning factor. Beaunis[8] felt that the reaction to pitch is the effect of experience and custom and cited a reversal among Orientals in whom low pitched sounds effect joyous reactions and the high, sadness and sorrow. _Intensity._ Heinlein found that loud chords are rarely soothing, and soft chords are almost always soothing. Beaunis stresses the fatiguing quality of great intensity over a long period, and contrasts it with “Very soft sounds as in Schumann’s ‘Danse des Sylphes’ ... which holds you under the charm of delightful emotion.”