求翻译：rhythm and blues first appeared on the music scene in the 1940's and evolved out of urban jazz and the blues.R&B was an umbrella term for the music industry that embraced all music written by musician that hit the chart.R&B continues to evolve today and has had a major impact on the creation of Motown and modern rock and on musical styles like rock and roll and pop. Today 's lesson explores the motown era of the 1960's as well as traditional urban singing games with roots in African American tradition是什么意思？

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