Scat singing is a vocal improvisation technique used in jazz music, where singers use nonsensical syllables and sounds instead of actual lyrics. This style allows performers to express emotions and creativity through rhythm and melody, often mimicking the sounds of instruments. The technique became popular in the 1920s, with artists like Louis Armstrong and Ella Fitzgerald showcasing their unique styles. Scat singing emphasizes spontaneity and can vary greatly from one performance to another, making each rendition a unique experience for both the singer and the audience.