What brought about the need or desire to notate music?
Music was an oral tradition in the same way stories were an oral tradition, passed on by "song-starters" and storytellers with well practiced capacious memories. For "consistency and precision," it became necessary to document the sounds that were being created. Early steps in notating music focused on naming the sounds being played and identifying relationships between sounds. As systems of musical notation developed, scales, keys, then notes became focused. Later the use of musical staves and different symbols to indicate the relative lengths of different tones gradually evolved.
The goal of these developments was to allow musicians to achieve consistency and uniformity in their performances of a given composition. Early forms of written music did not include the amount of specific information and structure that is provided by musical scores of today but were adequate for the musical requirements of their periods.