unique beauty and refinement of this form of art; and the more intelligent study of the Middle Age, which has now taken the place of the former prejudiced misinterpretation, is forming an attitude of mind that is capable of a sympathetic response to this most exquisite and characteristic of all the products of mediaeval genius. In order to seize the full significance of this school of Catholic music in its mature stage in the sixteenth century, it will be necessary to trace its origin and growth. The constructive criticism of the present day rests on the principle that we cannot comprehend works and schools of art unless we know their causes and environment. We shall find as we examine the history of mediaeval choral song, that it arose in response to an instinctive demand for a more expansive form of music than the unison chant. Liturgic necessities can in no wise account for the invention of part singing, for even today the Gregorian Plain Song remains the one officially recognized form of ritual music in the Catholic Church. It was an unconscious impulse, prophesying a richer musical expression which could not at once be realized,—a blind revolt of the European mind against bondage to an antique and restrictive form of expression. For the Gregorian chant by its very nature as unaccompanied melody, rhythmically controlled by prose accent and measure, was incapable of further development, and it was impossible that music should remain at a stand-still while all the other arts were undergoing the pains of growth. The movement which elicited the art of choral song from the latent powers of the liturgic chant was identical with the tendency which evolved Gothic and Renaissance architecture, sculpture, and painting out of Roman and Byzantine art. Melody unsupported soon runs its course; harmony, music in parts, with contrast of consonance and dissonance, dynamics, and light and shade, must supplement melody, adding more opulent resources to the simple charm of tone and rhythm. The science of harmony, at least in the modern sense, was unknown in antiquity, and the Gregorian chant was but the projection of the antique usage into the modern world. The history of modern European music, therefore, begins with the first authentic instances of singing in two or more semi-independent parts, these parts being subjected to a definite proportional notation.