What the early black music used by vocalists when they improvise?

The early black music used by vocalists when they improvise was called "scat singing." Scat singing is a vocal improvisation technique that uses nonsense syllables, such as "doo-wop" or "ba-da-ba," instead of actual words. It originated in jazz and blues music in the early 20th century, and has since been used in a variety of other genres, such as pop, rock, and R&B. Scat singing allows vocalists to express themselves freely and creatively without being constrained by the limitations of language.