Nabokov, Nicolas [Nikolay]

(v) Modal rhythm in practice.

The system of modal rhythm outlined by the theorists is an intellectual abstraction from flexible practice. The rudimentary patterns of the modes they cited are of course frequently encountered in the late 12th- and early 13th-century repertory, and are particularly clear in tenors of late clausulas and motets. But in practice they are often so extensively intermingled, not merely vertically in different voices but successively in single parts, that they are only of limited descriptive use if treated strictly. Modal integrity can be compromised not only by the insertion of unligated long notes within a phrase, but also by the practice of fractio modi (Lat.: ‘breaking of the mode’) – the introduction of shorter note values than normal. Such deviations alter the expected sequence of ligatures in a particular pattern. Fractio modi may have prompted an early formation of the 6th mode (6a) from the 1st, as the typical series of two-note ligatures succeeding an initial ternary figure in mode 1 is, in mode 6, replaced by three-note figures following an initial four-note gesture. In such cases the final note of the ligature tends to retain its normal value within the prevailing mode as far as is feasible, with the added notes splitting the other elements of the pattern. Even with this provision, however, the profusion of ‘non-modal’ ligatures in an ornate passage of fractio modi can seriously obscure a clear reading of the rhythm. Fig.49 gives some of the patterns described by Anonymus 4.

Ambiguities within the modal system may be demonstrated by two examples. Ex.9 gives the opening of the verse section of Perotinus's Alleluia, Posui adiutorium (I-Fl Plut.29.1, f.36v). Judging from the ligature patterns, both upper parts appear closest in form to the 2nd mode; yet the duplum lacks a final three-note ligature to match the triplum (which, contrary to the rules, ends with a two-note ligature followed by a single note). In this case, the penultimate note may reasonably be interpreted as a long. Consonances between the second note of each ligature, however, are greater in number than between the first – a transcription in the 1st mode thus seems more appropriate, so that each pulse is coincident with a consonance.

Ex.10 is from a Benedicamus Domino (I-Fl Plut.29.1, f.41r). Because of the prevalence of repeated notes, which defy ligation, the passage may be transcribed in the 6th mode (as in Husmann, 1940) as easily as in the 3rd. But most of the rest of the piece is in the 1st mode, so that a reading in the ‘alternative’ 3rd mode (3b) probably causes the least disruption. The consideration of variants in the concordant sources also influences interpretation, as, for example, in the third phrase where I-Fl Plut.29.1 notates the duplum in a 2nd-mode pattern, whereas D-W Guelf.628 (677) uses the 1st mode. Furthemore, cadences such as that in ex.10 frequently present problems of interpretation; the transcriptions given here are only a few out of many justifiable readings.



Notation, §III, 2: Polyphony and secular monophony to c1260

(vi) Organum purum, modus non rectus and irregular modes.

Particular segments of sustained-tone organum duplum (termed organum purum by Anonymus 4, and organum in speciali or organum per se by Garlandia) present serious problems regarding the extent and type of rhythmic interpretation and have caused much disagreement among scholars. Unlike discant or copula passages, whose unfolding often suggests a ‘straightforward’ (rectus) rhythmic mode, the ligature formations of organum purum defy such easy categorization. Garlandia's representative discussion of the rhythmic component, with its emphasis on oppositional construction, demonstrates vividly how the subsequent imposition of the modal system failed to reflect accurately the capricious style of organum purum:

Organum purum is said to be that performed according to a certain mode that is not rectus but non rectus. A rectus mode is used here to mean that by which discant is performed. … But in non rectus [measure] the long and breve are taken not in the first way, but according to the context (ex contingenti).

Just what contexts might affect the performance appear in a later paragraph:

Longs and breves in organum are recognized in this way, that is to say through [concord], through notation, through the penultimate. Whence the rule: each thing [?duplum note] that falls upon something [?tenor pitch] in compliance with the strength of the [consonances] is said to be long. Another rule: whatever is notated long according to the organa before a rest or in [?the] place [of a concord] is said to be long. Another rule: whatever is accepted before a long rest or before a perfect concord is said to be long.

Perhaps because of the vagueness of such passages, no agreement on the rhythmic realization of organum purum has yet been reached. Does the first rule imply that every harmonic interval between duplum and tenor owes its length to consonance, or only the contact points between the two parts at the start and close of major sections? Does the last rule apply to all perfect concords, or only particular ones? And what is the role of the notational component? What purpose do the duplum ligatures serve and how are they to be coordinated with the other strictures mentioned by Garlandia? Finally, and perhaps most importantly, there is the question of whether the theoretical information and manuscript sources reflect or recast a performing tradition that began at least a half-century earlier. Faced with such dilemmas it is easy to understand why editors of this repertory often choose a non-committal approach to organum purum by using stemless note heads, although several transcriptions with specified durations are also available (e.g. Waite, 1954; Tischler, 1988; Payne, 1996).

Another perplexing phenomenon are the ‘modi irregulares’ mentioned by Anonymus 4 (fig.50). While the first two appear to be rhythmically sharper versions of the normal 1st and 2nd modes, interpretations of the others ranges from binary mensuration of the long to mere nuances of tempo.

Notation, §III, 2: Polyphony and secular monophony to c1260