ligature

In music, a ligature is a compound note in mensural notation that indicates a group of musical notes to be sung to a single syllable. This notation evolved from neumes, which were early signs used to indicate the rise and fall of the voice in plainchant.12

During the 12th century, in France, neumes began to be drawn more thickly to represent multiple notes within a single syllable. This led to a rectilinear notation of heavy strokes and diamond-shaped dots, where groups of notes are called ligatures. These ligatures did not have a fixed rhythmic meaning; their pattern depended on the context. This system was used for troubadour songs, plainchant, and polyphonic music.2