Ligatures have two basic shapes:
box (rectangular) and
oblique (angled). Additionally, some ligatures have tails that either point up or down; the direction of the ligature's tail affects its meaning, unlike the direction of a tail on a modern note head. While primarily contextual, the system of ligatures in use from the 13th to the 16th century is fairly standardized. All ligatures of this period have the following principles in common: • All ligature notes are either the length of a
longa ("
L"), a
breve ("
B"), or a
semibreve ("
S"). • All ligatures have at least two notes. • For ease of discussion, ligatures of different lengths have different names. A ligature with two notes is called a
binaria; one with three notes, a
ternaria; one with four notes, a
quaternaria; and one with five notes, a
quinaria. Larger ones are possible, but rare. • If a ligature has three or more notes, all notes in the middle (the
mediae) are
B. • A downward tail changes the value of the note where the tail occurs, either from
L to
B or, less commonly, from
B to
L. • An upward tail indicates that the next
two notes are a series of
S. • A tail at the end of a ligature indicates an additional note be sung or played, called a
plica, that is not part of the ligature. Plicas were especially common with the rhythmic modes, to accommodate in practice what could not be accomplished within the very strict theoretical basis for modal music.
Alternate interpretations Most scholarship on ligatures is focused on period from the 13th to the 16th centuries. Prior to this period, ligatures were far less standardized; a
quaternaria ligature that, under the above rules, would mean a series like
SSLB would simply mean
BBBB. ==Transcription==