Before his time, all "recognized" music was a more or less melodious succession of tones, generally of the same length, one syllable being sometimes used for many notes. He discovered that a melody might be sung by several singers, each commencing at a different pitch instead of all singing the same notes at the same time. He also laid down rules as to how this was to be done to produce the best effect. We remember why he chose the fourth, fifth, and octave in preference to the third and sixth. He called his system an "organum" or "diaphony," and to sing according to his rules was called to "organize" or "organate." We must remember that at that time fourths and fifths were not always indicated in the written music; only the melody, which was called the principal or subject. By studying the rules prescribed for the organum, the singers could add the proper intervals to the melody. We must keep in mind, however, that later fourths were preferred to fifths (being considered less harsh), and that the musical scale of the period compelled the different voices to vary slightly, that is to say, two voices could not sing exactly the same melody at the interval of a fourth without the use of sharps or flats; therefore one voice continued on the same note until the awkward place was passed, and then proceeded in fourths again with the other voice as before: [G: {e' a'} {d' g'} {d' f+'} {d' e'}] On account of the augmented fourth that would occur by a strict adherence to the melodic structure of the subject, the following would have been impossible: [G: {e' a'} {d' g'} ({c' f+'})] Thus we find the first instance of the use of thirds, and also of oblique motion as opposed to the earlier inevitable parallel motion of the voices. This necessary freedom in singing the organum or diaphony led to the attempt to sing two _different_ melodies, one against the other--"note against note," or "point counter point,"[10] point or _punct_ being the name for the written note. There being now two distinct melodies, both had to be _noted_ instead of leaving it to the singers to add their parts extemporaneously, according to the rules of the organum, as they had done previously. Already earlier than this (in 1100), owing to the tendency to discard consecutive fourths and fifths, the intermovement of the voices, from being parallel and oblique, became _contrary_, thus avoiding the parallel succession of intervals. The name "organum" was dropped and the new system became known as tenor and descant, the tenor being the principal or foundation melody, and the descant or descants (for there could be as many as there were parts or voices to the music) taking the place of the organum. The difference between _discantus_ and _diaphony_ was that the latter consisted of several parts or voices, which, however, were more or less exact reproductions, at different pitch, of the principal or given melody, while the former was composed of entirely different melodic and rhythmic