Modes

MODES. - The word m. in music is used both in rhythmics and in harmony.

1) In the rhythmic sense it refers, in the music of the 12th and 13th centuries, to the six metrical patterns taken from classical prosody (trochaic, iambic, dactylic, anapestic; less frequent, spondee and tribrach) on which the "troubadours" modeled their songs. It is also applied to the durational value chosen as a unit: modus maior, represented graphically by the maxima, modus minor by the longa (both completely blackened); modus perfectus, ternary, modus imperfectus, binary. Often the key signature indicates (closed circle for perfect m., semicircle for imperfect m.) the nature of the chosen measure. This system holds in the music of the 15th and 16th centuries, written according to proportional notation. 2) In the harmonic sense, modern music knows two m.: major and minor, distinguished by the position of the two semitones in the scale of eight sounds: for the major the first semitone is two tones away from the fundamental, for the minor, instead, it is a tone and a half away. The tones are nothing but transpositions of the two modal successions, major and minor. 3) Through confusion one speaks of ecclesiastical or Gregorian "tones," whereas good terminology adheres to the word "m." for the harmonic systems that underlie the monodic compositions both of Greek music and of Western liturgical and medieval secular music.

Until the first decades of the 20th century the question of the Gregorian m. seemed resolved with the explanation of "complete and homogeneous" scales of 8 sounds. There was discussion only about the number of these scales, about their Greek or Oriental origin, whether they had an expressive character of their own, from which modal scale the modern major and minor had come to be formed. The Gregorian studies undertaken by the Solesmes school have brought to light quite other problems and have proposed objective solutions that are not negligible, if not entirely definitive. The first aspect of the modal question is summed up under the generic term of traditional theory (classical theory or theory of the octoechos); instead the questions that arose from about 1920 onward generally fall within the framework of modern theory or hexachordal theory.

I. TRADITIONAL THEORY

The theory of the eight modes, as it can be derived from the writings of medieval authors, is embodied in a few points. Although it is possible to construct a diatonic scale on each of the seven degrees of the scale, nevertheless only four are counted as fundamental, the famous tetrachord of the finals, re mi fa sol respectively for the modes protus, deuterus, tritus, tetrardus. Each of the scales results from the pairing of a fixed pentachord and a movable tetrachord: re-la + la-re, in protus. The mobility of the tetrachord above or below the pentachord makes possible the double form, authentic and plagal, of each of the four scales, which always retain the same final or fundamental; so that the authentic protus, 1st mode, extends from low re to high re, while the plagal protus, 2nd mode, goes from low la to high la; they are not two different scales, but two forms of the same scale, since the final is identical, that is, re in both cases; the difference is that a plagal melody unfolds in the lower part of this scale, while the authentic melody prefers the upper part. The ancient theorists do not have a concept as clear as the moderns of the existence and function of a dominant: the modern followers of the traditional system have considered the eight tenors (reciting tones) of the psalm formulas la fa do la do la re do as constructive data; they have introduced new elements by affirming the presence of the harmonic dominant (the fifth) not only in the authentic modes, but also in the plagal modes; they have applied to the repetition of the final in the upper octave of the authentic modes the same property of rest of the final as at the base of the scale, so that a double law would occur in Gregorian melodies: 1) of attraction toward the extreme notes as centers of rest (tonic-final-fundamental) in the authentic modes; 2) of repulsion from the extremes toward the center in the plagal modes.

Although the final notes are re mi fa sol, some melodies of the current editions, and many more in the diastematic manuscripts, cadence, definitively or provisionally, on the other three higher notes, that is, on la si do. Perhaps in order not to multiply the psalm formulas, but above all because the determination of the mode of a melody was made taking into account solely the species of the fixed pentachord (or tetrachord), the theorists did not hesitate to classify melodies on the final la si do, in protus, deuterus and tritus, despite the diversity of harmonic constitution with the modes of re mi fa. The greater importance recognized for the base tetrachord is confirmed by the few examples of modal analysis left by Ubald (Gerbert, Scriptores ecclesiastici de musica sacra, I, St-Blasien 1784, p. 140) and by Regino of Prüm (ibid., I, p. 231), who identify the modulations by referring to modal formulas; these formulas characteristic of the mode never reach the breadth of an octave, are generally content with a single semitone and go only slightly beyond the limits of the tetrachord.

The name of octoechos given to the theory of the eight modes suggests, together with other terms and peculiarities, a Byzantine importation into the Western system. Both the Byzantine and Western modal systems, as well as the traditional and modern theories, are indebted to the Hellenic musical modes, at least insofar as they have in common the base, that is, the tetrachord. In Gregorian chant itself, the melodies of deuterus (3rd and 4th modes with final mi and harmonic division fourth plus fourth, with la, the ancient "mese", as central pivot) can, without too much boldness, be reconnected with the Greek Dorian mode.

Table of the eight modes according to traditional theory.

II. MODERN THEORY OF THE THREE HEXACHORDS

Starting exclusively from the analysis of the melodies given in the Vatican edition of 1905 and 1907, Fr. J. H. Desroquettes, a monk of Solesmes, was the first to assert the existence of three groups of modal cadences in which the ancient melodist chose the harmonic material of his compositions.

He was followed in the systematization of the new theory by Prof. H. Potiron, organist, composer and theorist, and by Abbot Sufiol. The justification and explanation of the new system lies above all in the observation that medieval copyists base the cadences of the protus on re, on sol (with B-flat) and on la; the cadences of the deuterus on mi, on la (with B-natural); the cadences of the tritus on fa, on B-flat and on do; the cadences of the tetrardus on sol and on do. A single cadence note with a few intervals above and below it is enough to specify one of the four modes, which will then be authentic or plagal, taking into account the greater development above or below the fundamental; in a modal system understood in this sense, there is only one semitone: the appearance of a new semitone almost automatically determines a modulation: tonal, if in the new hexachord one remains in the same mode; tonal and modal, if in the new hexachord the mode also changes; for example, if, leaving the protus on re (natural hexachord), one modulates onto a cadence on la at the fifth, with B-natural, one passes into the hard hexachord and remains in the protus; if one goes to cadence on B-natural, the modulation is tonal (from the natural hexachord to the hard one) and modal (from the protus to the deuterus). Besides the appearance of a new semitone, insistence on intervals characteristic of a mode and the cadence outside the tetrachord of the modal notes likewise determine modulations.

The essential difference between this system and the traditional system consists in renouncing the classical structure of pentachord plus tetrachord, that is, the scale of seven consecutive diatonic sounds. The traditional theory was, at the outset, nothing more than an easy method of classification; the modern hexachordal theory claims more: it seeks to discover the modal principle of Gregorian melodic composition. While the traditional theory still distinguishes, like the Greeks, the various species of tetrachords (Dorian, Phrygian, Lydian), the modern theory, while always speaking of tetrachords, practically disregards the ancient distinction, since the tetrachord of the modal notes is not organic: in fact each of the four notes can be a final; but mi (la in the soft hexachord, si in the hard hexachord), even if it is a final, will not be considered as a fundamental; not only that, but the other three finals and fundamentals are not the starting point of a tetrachordal system recognizable later in the melodies. Thus the three tetrachords do-re-mi-fa, re-mi-fa-sol, mi-fa-sol-la are not distinguished, but it is the single tetrachord do-re-mi-fa that is repeated three times in the tonal diagram.

The importance of the modern theory is highlighted by the ease and coherence in the analysis of Gregorian melodies; on the other hand, it is believed that with this system the modal character of the melodies to be accompanied is not disfigured: the accompaniment must and can thus better follow the continual coming and going of the melody, which is almost never fixed either in a mode or in a key; of this the traditional theory is less conscious.

Diagram of the 4 modal cadences in the 3 hexachords.

The ethos, that is, the expressive character of the individual Gregorian modes, cannot be determined a priori: ancient and modern theorists do not agree on the psychological effect properly to be attributed, for example, to a 2nd or a 5th mode. The most varied texts and the most opposite feelings can be musically rendered in each of the eight modes; joy is not always and only illustrated with melodies of the 5th mode, nor sadness with melodies of the 2nd mode. It is true that a well-defined modal system modifies the expression of a given feeling and paints it with its own colors, but in Gregorian melodies, even in their most archaic form, frequent modulations at every moment soften the dominant impression that would result from the prevalence of one mode over the others.

Pietro Thomas