There are different he style of improvisational singing. The style of improvisational singing that this "First Lady of Song" was best known for having popularized is called scatting.
In scat singing, the singer open use improvises melodies and rhythms when using the voice as an instrument instead of speaking medium.
Fitzgerald was known for her unique ability to mimic instrumental sounds and this has helped make the vocal improvisation of scatting more popular.
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