rhythm and blues

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun plural A style of music developed by African Americans that combines blues and jazz, characterized by a strong backbeat and repeated variations on syncopated instrumental phrases.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a style of music combining elements of jazz and blues having syncopated rhythms and a strong backbeat; it was developed by African Americans in the late 1940s

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a combination of blues and jazz that was developed in the United States by Black musicians; an important precursor of rock 'n' roll