Rhythm and blues
Large jazz bands had begun to replace traditional blues, which had begun to move to the underground music scene. Southwestern "shouting" blues singers developed into a style called rhythm and blues, which was largely huge rhythm units smashing away behind screaming blues singers. The performance of the artists became just as important as the performance of the songs. Rhythm and blues, despite its growth in popularity, remained a "black" form of music that had not yet reached the level of commercialism where it would be popular in the white community. The more instrumental rhythm and blues use of large instruments complemented the traditional vocal style of classic blues. It however differed from traditional blues by having more erratic, louder percussion and brass sections to accompany the increased volume of the vocals. Rhythm and blues had developed into a style that integrated mainstream without being mainstream. With its rebellious style, rhythm and blues contrasted the mainstream "soft" nature of Swing with its loud percussion and brass sections, and because of its distinctive style remained a predominantly "black" form of music that catered to an African American audience. There was divide however between the middle class of African Americans, who had settled upon mainstream swing and the lower class, who still had a taste for traditional country blues. Over time, the mainstream sounds of swing became embedded so far into rhythm and blues that it became indistinguishable from its country blues roots and into a commercialized style.