With the simultaneous employment of more than one voice, music passed out of its infancy. The Polyphonic period, so called from Greek words signifying “many-voiced,” extended, through all the Middle Ages, up to so recent a date as the end of the sixteenth century, there to culminate in the remarkable compositions of Palestrina. In duration it was the longest of all the periods; but this is not surprising when we consider, in the first place, the almost insuperable difficulties to be overcome before even two voices could be pleasantly and fluently conducted together; in the second place, the absence of all prototypes or models for the first experimenters to work from; and, above all, the surprising distance that separates Palestrina’s ingenious, intricate, and beautiful tone-fabrics, written sometimes in as many as sixteen parts, from the rude and protoplasmic chants of two voices, singing an interval of a “fifth” apart, from which they were developed. That type of chant in which two voices, one a fifth higher than the other, sang the same melody, primitive as it was, and intolerable to modern ears, was to its originators a convenient and pleasant device. It was convenient because, the natural range of soprano and tenor voices being about a fifth above that of contraltos and basses, choirs could chant at this interval more naturally than at the octave. It was pleasant because, while it left each of the two melodies distinctly audible, it produced by their combination a harmonic richness that must have fallen on mediæval ears with an unwonted splendor. Organum, as this device of singing in fifths was called, must be ever memorable in the history of music as the beginning of harmony.