Plica
An ornamental sign of medieval notation.
What it means
The plica — “fold” — is a sign of medieval notation that attaches an additional note to a written note. This additional note is not separately notated but indicated by a stroke on the note sign; its direction — upward or downward — results from the position of the stroke. It counts as a passing note or connection to the following note, not as an independent part of the melody.
In the notation
The plica is recognizable by an additional stroke on the notehead that goes beyond the usual measure; if it points upward, a higher additional note is meant, downward a lower one. In ligatures it usually appears as a vertical stroke on the final sign (ligatura plicata). The pitch of the additional note follows from the main note and the next note: if both are the same, the upper or lower neighbour is meant, depending on the direction of the stroke; if they lie a third apart, the additional note fills the gap as a passing note; in all other cases the musical context must decide.
Musical use
The sign was widespread in the music of the twelfth and thirteenth centuries, in monophonic chant as well as in early polyphony. A connection is suspected with a particular manner of performance: the additional note is thought not to have been attacked like an ordinary note but formed out of the main note, as it were as an afterbeat or gliding motion. What this sounded like exactly cannot be established with certainty from the sources; the interpretation of the sign belongs among the open questions of the study of notation. The sign derives from the liquescent neumes of chant, such as the cephalicus. It remained in use in the mensural notation of the thirteenth century, where it was attached to the longa and the breve; the additional note usually represents a breve added on a weak beat.
Performance practice
If a modern edition writes out plica notes, do not treat them as melody notes of equal standing: they hang on their main note and lead on to the next one. Sing them lightly and without a new attack, with the weight on the main note. Check in the critical report whether the edition takes the pitch of the additional note from the source or has inferred it — both occur, and in the second case the reading is a suggestion.