I not gonna use that expression in case anyone blocks me, but I currently have on
Cash Money & Marvellous - New Sheriff In Town, which is definitely O - S hip-hop, and the term has been used with hip-hop for about 20 years, I have hip-hop albums using that term in their name from over 15 years ago.
Going back to an earlier comment on the thread, what's wrong with Christina Aguilera, admittedly very commercial and not everyone's cup of tea, but she has a damn fine voice.