How did plainchant notation allow flexibility and regional variation in performance?

Plainchant notation, specifically the use of neumes, facilitated flexibility and regional variation because early systems were primarily designed as memory aids rather than precise instructions for performance.12

Because these early, staffless (chironomic) neumes only indicated the general direction of a melody—rising or falling—rather than exact pitch or duration, they relied heavily on the singer's prior knowledge of the melody and text. This semi-oral tradition allowed for significant regional interpretation, as different geographical areas developed their own distinct systems of neumes and performance practices.12

Furthermore, the rhythm of plainchant was not governed by a rigid, standardized meter but was instead tied to the natural accentuation and dynamic flow of the Latin text. This "free" rhythmic approach, combined with the lack of precise pitch notation, meant that tempos and melodic details could vary according to the specific occasion or local tradition. It was only later, with the development of "heighted" neumes and the eventual adoption of the musical staff, that notation began to provide the precision necessary to standardize melodies across different regions.3412