Musical composition can refer to an original piece of music, either a song or an instrumental music piece, the structure of a musical piece, or the process of creating or writing a new song or piece of music. People who create new compositions are called composers in classical music. In popular music and traditional music, the creators of new songs are usually called songwriters; with songs, the person who writes new words for a song is the lyricist.
"Composition" is the act or practice of creating a song or other piece of music. In many cultures, including Western classical music, the act of composing typically includes the creation of music notation, such as a sheet music "score", which is then performed by the composer or by other instrumental musicians or singers.
In popular music and traditional music, songwriting may involve the creation of a basic outline of the song, called the lead sheet, which sets out the melody, lyrics and chord progression. In classical music, orchestration (choosing the instruments of a large music ensemble such as an orchestra which will play the different parts of music, such as the melody, accompaniment, countermelody, bassline and so on) is typically done by the composer, but in musical theatre and in pop music, songwriters may hire an arranger to do the orchestration.
In some cases, a pop or traditional songwriter may not use written notation at all, and instead compose the song in her mind and then play, sing and/or record it from memory. In jazz and popular music, notable sound recordings by influential performers are given the weight that written or printed scores play in classical music.