The modern name for a medieval concept of rhythm in which the value and relative duration of each note is determined by its position within a larger rhythmic series, or mode, consisting of a patterned succession of long and short values. In notation, the value of the individual note is communicated not by the form of the note but by its position within a larger figure of notation (called a ligature, a group of pitches ‘bound’ together) and by the position of that figure among other figures. This is the earliest known coherent system of rhythm and rhythmic notation in Western music since antiquity. It was associated primarily with the polyphony of the Notre Dame school of the late 12th century and the early 13th, but some modern scholars have also applied it to medieval secular monophony, albeit with questionable results.
The rhythmic modes are described in a group of treatises from the 13th century, most importantly the De mensurabili musica of Johannes de Garlandia (ed. Reimer, 1972); the texts of the St Emmeram Anonymous (ed. and trans. Yudkin, 1990) and Anonymous IV (ed. Reckow, 1967) that are based on Garlandia; Anonymous VII (CoussemakerS, i); the anonymous Discantus positio vulgaris (ed. Cserba, 1935); Lambertus (CoussemakerS, i); and Franco of Cologne (ed. Reaney and Gilles, 1974). Like the Notre Dame repertory in which it is found, modal rhythm developed before the advent of mensural note forms, but all the theoretical witnesses draw upon mensural notation to reduce the ambiguity inherent in the system. Thus the original form of the system must be reconstructed to a certain extent; it can be seen in operation in a number of 13th-century manuscripts (e.g. D-W 628, E-Mn 20486 and I-Fl Plut.29.1; see Sources, MS, §IV, 4.).
Johannes de Garlandia defined modus or maneries (‘style’, ‘kind’, ‘type’; the terms are borrowed from writings on logic, but modus has a long history in music theory as well) as ‘that which flows together [concurrit] by the measurement of time, that is, by longs or by shorts’ (Reimer, p.36). These ‘long’ and ‘short’ values are precisely measured, and the ‘measurement of time’ consists in the reiteration of a succession of such values in a given pattern. Garlandia presented six such modal patterns, all subsumed within a single system by a common unit of measure, the tempus (‘temporal unit’), that was regarded as ‘indivisible’, that is, incapable of being divided into precisely measurable shorter values. Through this constant, the different values are related to one another (‘flow together’), and the six modes can be combined with each other in a polyphonic texture.
Garlandia’s six rhythmic modes were (L= long, B = breve): (1) L–B–L–B–L etc.; (2) B–L–B–L–B etc.; (3) L–B–B–L–B–B–L etc.; (4) B–B–L–B–B–L–B–B etc.; (5) L–L–L etc.; (6) B–B–B–B etc. Although the modal patterns are theoretically infinite in length, in practical terms they are always delimited, usually by a rest, but sometimes by juxtaposition with another pattern or some other kind of interruption. Such a temporally delimited pattern is called an ordo (‘arrangement’). A statement of the modal pattern is ‘perfect’ (complete) when the ordo ends with the same value as the one with which it begins; it is ‘imperfect’ (incomplete) when it ends with some other value (in the case of mode 4, the perfect form ends with a restatement of the first two values). The rest that ordinarily follows and defines an ordo has the value of the next duration in the pattern, be the mode perfect or imperfect.
A breve of one tempus and a long of two tempora were regarded as the normal values, and are referred to as ‘regular’ (recta) and as defining proper measure (recta mensura); hence, the three modes that use them exclusively (1, 2 and 6) are termed the ‘measurable’ modes (see ex.1). The orderly succession of longs and breves in these modes sets up an intrinsically ternary pulse, although metre is not an explicit part of modal theory. Modes 3, 4 and 5 proceed in the same ternary fashion; the long is equal to three tempora, not two, and the second of the two successive breves in modes 3 and 4 (the altera, ‘other’ breve) is equal to two tempora. The altera thus has the same duration as the recta long; it is a breve (short note) in comparison with the long that follows it. Values other than the ‘regular’ ones – the long of three tempora, the brevis altera of two, the duplex long of six, and the semibreve – were deemed ‘beyond (regular) measure’ (ultra [recta] mensuram), that is, as standing outside the group of ‘normal’ long and short durations; the modes that use them (3–5) are called modi per ultra mensuram (‘modes by virtue of values beyond conventional measure’); one version of Garlandia’s treatise calls them ‘oblique’ modes (see ex.2). Taken together, Garlandia’s six modes constitute a complete, closed system, accounting in patterned terms for all possible combinations of rhythmic values that could occur in the musical practice of the Notre Dame tradition.
The rhythmic modes were expressed in writing using the ligatures (neumes) and single notes of the ‘square’ plainchant notation developed in France during the 12th century. Each mode was identified by a particular succession of ligatures and single notes, as follows: 1st mode: 3–2–2 … 2; 2nd mode: 2–2–2 … 3; 3rd mode: 1–3–3 … 3; 4th mode: 3–3–3 … 2; 5th mode: 1–1–1 … 1 (or 3–rest–3–rest–3 … 3); 6th mode: 4–3–3 … 3. Ex.3 gives examples of the second ordo of each of the modes (note that, depending on the mode, a ‘2’ can be read in three different ways, a ‘3’ in five). Since a ligature cannot have more than one syllable of text, the mode-conveying ligature patterns are clearly evident only in a melismatic context (sine littera); in passages with frequent changes of syllables (cum littera) the sequences of ligatures are broken up, thereby posing severe problems of interpretation (as they did in the 13th century, according to Anonymous IV). Repeated pitches, which also cannot be accommodated within a single ligature, can further disrupt the profile of the ligature pattern.
The strict patterns of the modes could be modified in various ways. Shorter values might be substituted for one or more of the longer ones, giving in mode 1, for example, L–S–S–L–B–B–B–B–L (S = semibreve). Garlandia termed this practice ‘reduction’, but Anonymous IV called it fractio modi (‘breaking of the mode’). Or, as another type of reductio, longer values could replace two or more shorter ones, in mode 2, for example, giving B–L–L (ultra mensuram)–B–L–B–L–L (ultra mensuram). Especially common is an extended form of the first mode that proceeds L (ultra mensuram)–L–B–L (ultra mensuram)–L–B–L (ultra mensuram) etc.; the notation of this pattern looks like that of the third mode (in fact, it is often considered to be an ‘alternative’ form of the third mode; Anonymous IV called it an ‘unusual mode, like the irregular ones’). A phrase might shift from one mode to another without a break, a practice called ‘admixture’ by Anonymous IV; thus the pattern L–B–L–B–B–L–B–L–B shifts from mode 1 to mode 2. The unpatterned ligatures and florid, often rapidly moving lines of organum purum were described by Johannes de Garlandia as being in a modus non rectus (‘unconventional mode’) in which the rhythmic values are not determined by their relationship to a mode, as they are in the modus rectus and recta mensura (‘regular measure’) defined by the modal patterns; Anonymous IV called this unpatterned style a ‘thoroughly mixed and common mode’. Anonymous IV, again in connection with organum purum, described a series of ‘irregular’ modes in which the porportional relationships among the values are distorted, in effect presenting performance liberties such as tenuto, accellerando and ritardando in modal, patterned terms. Just as the imperfect modes were developed to accommodate, for example, hocket and the intrusion of new syllables of text into an orderly succession of ligatures, all of these modifications and extensions served to relate the modal system to the realities of musical practice.
The modal doctrine laid the foundation for the European rhythmic language and its expression in notation for the next four centuries; its importance cannot be overestimated. Various theories have been proposed to explain the origins of the rhythmic modes and their relationship to musical practice. Waite (1954) argued that Leoninus developed the modal system, and that he used Augustine’s De musica as a model. Others believe that modal rhythm emerged spontaneously in the music of the 12th century (Treitler, 1979; Crocker, 1990; Roesner, 1990). It seems likely that the ‘rhythmic modes’ as such arose as a theorectical synthesis of a pre-existing, broader polyphonic practice; once formulated, the modes could have served as models for subsequent composition and for the reinterpretation of earlier, less strictly ‘modal’ works. What role antique and contemporary poetry or poetic theory may have played in the development of the modal system is not yet entirely clear.
After Johannes de Garlandia, several theorists sought to include the semibreve in the modal system, and thereby to accord it precise measure. Lambertus extended the rhythmic modes to nine, including four patterns that describe various combinations of breve and semibreve motion; in effect, the hitherto ‘indivisible‘ recta breve became ternary. In his Ars cantus mensurabilis Franco of Cologne described five modes, combining Garlandia’s modes 1 and 5 into one and re-defining Garlandia’s mode 6 as expressing movement ‘entirely in breves and semibreves’ (thus subsuming four of Lambertus’s modes into one). A seven-mode system, alluded to but rejected by Franco, is mentioned in the 14th-century treastise once attributed to Theodoricus de Campo; the seventh mode moves entirely in semibreves. For Franco, and for musicians following him, however, the modes were used not as guides to the notation, but exclusively as descriptions of durational relationships; unequivocal mensural notation had taken over the former task from the rhythmic modes.
See also Notation, §III, 2; Rhythm, §II.
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For further bibliography see Notation and Organum and discant: bibliography.
EDWARD H. ROESNER