Mensural Notation - Ligatures

Ligatures

Ligatures are groups of notes written together. They were a holdover from the modal rhythmic system which preceded mensural notation, and they retained some of the original rhythmic meaning they had had there.

The origins of ligature semantics can be found in a rhythmical re-interpretation of the ligature neumes used since much earlier in the notation of Gregorian plainchant. In modal notation, ligatures had been used to represent stereotyped sequences of short and long notes, grouping notes together in much the same way as metric feet are used to group short and long syllables in Latin poetry. The most basic rhythmical unit was felt to be a group of one short and one long note (brevis-longa), like an iamb in poetry, filling an upbeat pattern in the typical 6/4 meter mentioned above. All other two-note groups were classified in terms of deviation from this basic pattern. In medieval terminology, a two-note ligature possessed "propriety" (proprietas) if and only if its first note was short; and it possessed "perfection" (perfectio) if and only if its second note was long. (Note that this sense of perfection is unrelated to the issue of perfect vs. imperfect in the sense of triplex vs. duplex duration of the long note as discussed above.)

1. Accordingly, a note pair cum proprietate et cum perfectione could be written with the most basic of ligature shapes, those inherited from plainchant, namely the descending clivis and the ascending podatus.
2. If, by way of exception, the first note was to be long (sine proprietate), this was signaled by a reversal of the use of stems: leave out the stem of the descending clivis; add a stem to the ascending podatus.
3. If, conversely, the second note was to be short (sine perfectione), this was signaled by a change in the noteheads themselves: replace the descending sequence of square heads with a single diagonal beam; fold out the second note of the ascending to the right.
4. If both exceptions co-occurred (sine proprietate et sine perfectione), both graphical alterations were combined accordingly.
5. In addition to sequences of a longa and a breve, ligatures could also contain a pair of semibreves (but never a single one). These were called cum opposita proprietate, and consistently marked by an upward-pointing stem at the left of the note pair.

In the course of time, some alternate versions of the ascending ligatures were developed (last column). Thus, the basic ascending podatus shape was replaced by one where the second note was both folded out to the right, and marked with an extra stem (two alterations cancelling each other out, as it were). The ascending L-L (sine proprietate) was modified accordingly. Some confusion consequently arose about how to write an ascending L-B or B-B (sine perfectione). This, in the end, was the only area of ligature notation that was controversial among contemporary theoreticians, with some authors prescribing one set of values to two ligature shapes, and other authors just the reverse.

For ligatures of more than two notes, the following rules hold:

• Any notehead with an upward stem to its left is the first of a pair of semibreves (cum opposita proprietate).
• Any medial notehead with a downward stem to its right is a longa.
• A prolonged, double-wide notehead with a downward stem to its right is a maxima.
• Any other notehead not covered by any of the rules above is a brevis.
• The perfect or imperfect duration of each note within a ligature is determined according to the same principles as for the standalone notes.

By the late 15th century, the most common ligatures by far were those cum opposita proprietate (S-S), but all were still in routine use.