The blues & jazz both draw from a wellspring of similar roots in African-American popular music & culture. The paths of each genre have diverged widely since the early 1900s, but before 1950, the styles were deeply intertwined with each other. It's a marriage that will endure to some degree as long as blues and jazz are around. The most active period of cross-fertilization between blues and jazz may have been the 1930s and 1940s, when swing and big band styles were at their peak, and when the blues was moving toward a fuller and more citified sound. Jazz was still often played in dance halls, and needed some singers and song structures to help maintain its accessibility. Blues was moving toward a more sophisticated sound that would soon encompass full bands and electricity. Each form had much to learn from the other. Several of the early big bands featured vocalists that not only borrowed from the blues in their songs and phrasing, but in turn influenced the evolution of other bluesmen. Jimmy Rushing, in his work with Count Basie, may have been the first notable blues-based singer to front a big band with a precursor to the "shouting" style. This was developed to its fullest shortly afterwards by singers with Kansas City-based swing bands, including Big Joe Turner, Jimmy Witherspoon, and Walter Brown. Along w;the shouters the main tributary of blues feeding into jazz was found in the boogie-woogie pianists of the late '30s and early '40s. The famed Spirituals To Swing concerts in New York City's Carnegie Hall in the late 1930s found the marriage between the idioms at their peak featuring the wild sax solo of Illinois Jacquet in Lionel Hampton's "Flying Home" rates as a leading forerunner of R&B, particularly the "honking" style of sax associated with the form. The shouters, honkers, and boogie-woogie would coalesce in the 1940s into jump blues, which in some senses was the ultimate jazz-blues fusion.