John Birks "Dizzy" Gillespie was an American jazz trumpet player, bandleader, composer and singer. Gillespie was a trumpet virtuoso and improviser, building on the virtuoso style of Roy Eldridge but adding layers of harmonic complexity previously unknown in jazz. His beret and horn-rimmed spectacles, his scat singing, his bent horn, pouched cheeks and his light-hearted personality were essential in popularizing bebop.