“Composition” is often classed as the creation and recording of music via a medium by which others can interpret it (i.e., paper or sound). Many cultures use at least part of the concept of preconceiving musical material, or composition, as held in western classical music. Even when music is notated precisely, there are still many decisions that a performer has to make.
The process of a performer deciding how to perform music that has been previously composed and notated is termed interpretation. Different performers’ interpretations of the same music can vary widely. Composers and song writers who present their own music are interpreting, just as much as those who perform the music of others or folk music.