 In jazz, which is mostly improvised, sheet music (called a "lead sheet" in this context) is used to give basic indications of melodies, chord changes, and arrangements.Even when a jazz band has a lead sheet, chord chart or arranged music, many elements of a performance are improvised.Handwritten or printed music is less important in other traditions of musical practice, however, such as traditional music and folk music, in which singers and instrumentalists typically learn songs "by ear" or from having a song or tune taught to them by another person.