The freer and more promising style which issued from the treadmill of the organum was called in its initial stages discant (Lat. _discantus_), and was at first wholly confined to an irregular mixture of octaves, unisons, fifths and fourths, with an occasional third as a sort of concession to the criticism of the natural ear upon antique theory. At first two parts only were employed. Occasional successions of parallel fifths and fourths, the heritage of the organum, long survived, but they were gradually eliminated as hollow and unsatisfying, and the principle of contrary motion, which is the very soul of all modern harmony and counterpoint, was slowly established. It must be borne in mind, as the clue to all mediaeval music, that the practice of tone combination involved no idea whatever of chords, as modern theory conceives them. The characteristic principle of the vastly preponderating portion of the music of the last three centuries is harmony, technically so called, _i.e._, chords, solid or distributed, out of which melody is primarily evolved. Homophony, monody—one part sustaining the tune while all others serve as the support and, so to speak, the coloring material also—is now the ruling postulate. The chorus music of Europe down to the seventeenth century was, on the other hand, based on melody; the composer never thought of his combination as chords, but worked, we might say, horizontally, weaving together several semi-independent melodies into a flexible and accordant tissue.[64]