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.
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.
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.
[3] 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.