Carmen McRae

Very often with famous entertainers, only the first name is sufficient for identification. This happens particularly in the genres of jazz and standard/popular music. When a hip person wants to say something about a well-known artist, they may refer to that artist as Sarah, Billie, Ella, or Carmen. The latter of course is a reference to Carmen McRae, dubbed by jazz critics, writers and fans, "The Singer’s Singer."  

Carmen McRae: The Great American Songbook