Theorists give us our first firm information on Western polyphony. The Musica enchiriadis, around 900, gives directions how to sing in parallel with a chant, above or below at fourth, fifth, or octave, or consonant combinations of these intervals. From the performer’s point of view, such singing in parallels means singing the same chant but starting a fourth, fifth, or octave away from the normal pitch. But from the listener’s point of view, singing in parallels produces a series of very resonant sonorities with a single melodic profile—the profile of the original chant. This effect would have been especially marked under the acoustical conditions, the kind of architecture, in which such singing was done. Perfect consonances such as fifth and octave (which, being sung, could be made pure rather than tempered) are, of course, essential to producing such resonance; false intervals such as augmented or diminished fifths or octaves would cause an immediate and disturbing disruption of the resonance. Singing in parallels added nothing to the original chant except rich sonority; it introduced no new structural element. This kind of singing undoubtedly went back a long time and continued unchanged for centuries. It was in common use during the 900s, especially for the singing of modern chant such as hymns and proses. The Musica enchiriadis also describes a way of singing at the fourth below, in which the added voice begins in unison with the original chant, but repeats the same pitch while the original chant ascends, until the two voices are in fourths. Proceeding in fourths until the end of the phrase, the added voice arrives at a unison in an analogous way. This use of oblique motion results in a varied series of less consonant intervals—seconds and thirds—in between the initial and final unisons and the parallel fourths. While the increase in complexity over parallels is slight, and the artistic gain negligible, nonetheless a very important change in principle is here evident. The shape of the original melody may still guide the progression of intervals, but it is no longer the only factor in that progression. The progression of intervals, from unison through second and third to fourth, is subject to a whole new realm of considerations having to do with relative qualities of intervals, relative degrees of consonances. The resulting progression may still reinforce the phrase shape of the chant, may still be an analog of the original melody, but from this moment on it becomes increasingly an analog, not an identity as before. Clearly the exploitation of interval progressions depended on hearing a great many experiments, both successful and otherwise. There were no rules in existence; they had to be arrived at pragmatically. Just as clearly, exploitation was maximized when the kind of motion was as far from parallel as possible. If parallel motion produced identical intervals in succession, then a varied succession of intervals must be produced by contrary motion. Between 900 and 1100 there must have been extensive, if sporadic and mutually isolated, experiments in handling contrary motion. Of these experiments but little record remains.
Early Roots of Western Musical Influence in Persia
