Why is the notation for Gregorian Chant so different from modern five-line notation?
Because it comes from the Middle Ages. Notation has varied a lot throughout history. For many centuries, the entire chant repertoire was known by heart and no notation was used. The earliest notation, used only by the conductor, was little squiggles which suggested the general shape of the melody to remind the conductor of what was known by heart. Up until the late Middle Ages, singers sang without any music-think of how confidently and freely they must have been able to sing! Conductors, however, needed more help to remember the melodies, and gradually one and then more staff lines were added to indicate the exact pitch. Four lines became standard by about the thirteenth century, and four-line notation has been customary ever since. Square note heads as used in what is now France eventually became the notation used and printed everywhere. This four-line, square note notation has one major advantage over our modern five-line notation: it groups many notes closely together over one syll
