Improvise, in jazz, is a term used to describe the act of creating music spontaneously. VAMP, which is four letters, is a repeating musical phrase or figure that is used as a background for improvisation. FAKE, also four letters, is a method of playing jazz by reading from a lead sheet, which contains the melody and chords of a song. Finally, SCAT, also four letters, is a vocal improvisation technique in which the singer uses nonsense syllables instead of words. All of these techniques are used to create improvised jazz music.