thumb|Box and oblique ligatures (13th to 16th century); see [[#Usage|usage, below]]
In music notation, a ligature is a graphic symbol that tells a musician to perform two or more notes in a single gesture, and on a single syllable. It was primarily used from around 800 to 1650 AD. Ligatures are characteristic of neumatic (chant) and mensural notation. The notation and meaning of ligatures has changed significantly throughout Western music history, and their precise interpretation is a continuing subject of debate among musicologists.
History
Plainchant
The early notation of plainchant, particularly Gregorian chant, used a series of shapes called neumes, which served as reminders of music that was taught by rote rather than as an exact record of which notes to sing. Neumes were in use from the 9th through the 11th centuries AD for most plainsong, and differed by region.<!--In the passage in question, Apel is primarily discussing ligatures, which he says "developed from certain neumes ... such as were in use during the ninth, tenth, and eleventh centuries", but also says, "When (around 1150 [i.e., the middle of the twelfth century] ther neumes changed to the more definite forms of the so-called Roman chorale notation, these four signs took on the following shapes: [illustration]. These forms are still used today...". He says nothing about different regional styles, and the discussion of neumes is confined to p. 88.--> Due to their malleable nature, there were no hard and fast rules for the lengths each note was supposed to last, or even how high or low the intervals between notes were to be.
De mensurabili musica
A treatise on notation named De mensurabili musica was copied around 1260. In this treatise, the anonymous author proposed that, much in the same way that poetry of the time was based on a series of modal rhythms, music should also be set up in this way. The notation of these modes was accomplished primarily through using ligatures in varying lengths and with varying degrees of complexity, where the rhythms would be derived from context. For most of their notated history, this was the purpose of ligatures: to indicate the rhythmic mode.
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
In transcribing old works to modern notation, where no compound graphs as ligatures exist, editors usually indicate by a hook, a bracket (brace), or (less often in polyphonic music) a slur/phrase mark those notes that the original combined into a ligature. To avoid confusion, many scores transcribed purely for performance do not include additional notation to indicate that a particular note originally belonged to a ligature, as most methods to show this have separate meanings in a performance capacity.
See also
- Legato