Musical composition can refer to an original piece of music, the structure of a musical piece, or the process of creating a new piece of music. People who practice composition are called composers.
Although today composition is considered to consist of the manipulation of each aspect of music (harmony, melody, form, rhythm, and timbre), according to Jean Benjamin de Laborde (1780):
Composition consists in two things only. The first is the ordering and disposing of several sounds...in such a manner that their succession pleases the ear. This is what the Ancients called melody. The second is the rendering audible of two or more simultaneous sounds in such a manner that their combination is pleasant. this is what we call harmony, and it alone merits the name of composition.