Simplify the following text for a Grade 9 native English-speaking person.
Original: The advent of bebop led to new developments in Fitzgerald 's vocal style , influenced by her work with Dizzy Gillespie 's big band . It was in this period that Fitzgerald started including scat singing as a major part of her performance repertoire .
Simplified: She worked with Dizzy Gillespie 's big band and started including scat singing as a big part of her performances .