In the UK any contemporary black music that isn't easily definable, e.g. reggae or rap, is called R'N'B*. I prefer to refer to individual acts rather than genres, but if you're talking to someone who doesn't , ahem , share your knowledge then labels save a lot of time.
*BTW I've never heard the initials R'N'B explained in it's modern form.
PS Weren't The Marcels a mixed race group ?.