Scat singing is a form of improvisational singing that involves vocalizing nonsense syllables and words. It is often used in jazz music and is characterized by its use of melodic improvisation, vocalized rhythms, and vocal sounds that imitate instruments. The term 'SCAT' comes from the phrase 'SCAT singing, ' which was first used in the 1930s. SCAT singing is a popular form of improvisational singing that has been used by many famous jazz singers, such as Ella Fitzgerald and Louis Armstrong.