Scat chorus

A scat chorus is an example of Mouth music: in other words a string of meaningless syllables that carry a melody such as do-wah-diddy-diddy-dum-diddy-doo or ooh-eee-ooh-ah-ah-ting-tang-walla-walla-bing-bang, though it's often improvised on the spot, rather than codified as those two examples. Ella Fitzgerald, among others, was known for scat singing.