A musical composition is a piece of original music designed for repeated performance (as opposed to strictly improvisational music, in which each performance is unique). The music may be preserved in memory, or through a written system of notation. Compositions include songs to be performed by human voices, usually including lyrics, as well as pieces written for other musical instruments.
Musical composition may also refer to the process by which a piece of music is originated. People who practice composition are called composers. Useful skills in composition include writing musical notation, instrumentation, and handling musical ensembles (orchestration).
Important in much musical composition or musical form is the scale for the notes used, including the mode and tonic note. Whereas when playing or reading music, only the key signature (set of notes in scale) matters. In music using twelve tone techniques the tone row is even more comprehensive a factor than a scale.