With the spread of Dixieland, jazz music began to change. Around 1920 the saxophone became a mainstay within the ensemble; before 1920 the melody or soprano saxophone had been used in place of the clarinet in few bands. The focus on group improvising, which had been the mainstay of the Dixieland style, began to give way to the soloist. Players such as Louis Armstrong were key in this development; while he had started out as a Dixieland player, Armstrong’s playing had the ability to outshine the rest of the ensemble. His brief solos and improvisations within the ensembles created the need for the extended solo. With the extended solo, there came the requirement for written arrangements; the ensemble players needed to know when a solo when end and the music that was to take place afterwards. With these arrangements the music began to take on new qualities of rhythm and orchestration that led to the development of swing.