Although a musical composition often uses musical notation and has a single author, this is not always the case. A work of music can have multiple composers, which often occurs in popular music when a band collaborates to write a song, or in musical theatre , when one person writes the melodies, a second person writes the lyrics, and a third person orchestrates the songs. In some styles of music, such as the blues , a composer/songwriter may create, perform and record new songs or pieces without ever writing them down in music notation. A piece of music can also be composed with words, images, or computer programs that explain or notate how the singer or musician should create musical sounds. Examples range from avant-garde music that uses graphic notation , to text compositions such as Aus den sieben Tagen , to computer programs that select sounds for musical pieces. Music that makes heavy use of randomness and chance is called aleatoric music , and is associated with contemporary composers active in the 20th century, such as John Cage , Morton Feldman , and Witold Lutosławski . A more commonly known example of chance-based music is the sound of wind chimes jingling in a breeze.