He then spent eight months playing drums and the vibraphone in Claude Hopkins's group, before Gillespie gave Clarke an opening to join him in the Teddy Hill band in the Savoy Ballroom in 1939. While playing for this group on a fast tune, he came upon the idea of using the ride cymbal on his right hand to keep time rather than the hi-hat, an approach that freed up his left hand to play more syncopated figures. On the bass drum he played irregular accents (dropping bombs), while using the hi-hat on the backbeats, adding more color to his drumming. With Gillespie, who encouraged this new approach to time keeping, Clarke wrote a series of exercises for himself to develop the independence of the bass drum and snare drum, while maintaining the time on the ride cymbal. One of these passages, a combination of a rimshot on the snare followed directly by a "bomb", reportedly inspired Clarke's nickname, "Klook", which was short for "Klook-mop", in imitation of the sound this combination produced. At the 1939 New York World's Fair, Clarke played opposite a band led by fellow drummer Chick Webb, who strongly influenced him and encouraged his rhythmic explorations. He was briefly fired from Hill's band due to unrest in the trombone section about his unorthodox time-keeping methods, but later returned and stayed with the group until it disbanded in 1940. He then worked with bands led by Sidney Bechet, Ella Fitzgerald (where he and Gillespie are said to have co-written the composition "Salt Peanuts"), and Louis Armstrong, before working with Roy Eldridge once again along with the Count Basie Orchestra. He also made recordings with Bechet, Fitzgerald, and Mildred Bailey.