Ronnie Milsap, who in recent years turned into one of country-pop's wimpiest ballad singers, has recovered from his Barry Manilow phase, only to fall victim to a Black Attack. Milsap may have done whitewashed R&B in the past, but now he suffers from serious Isaac Hayes delusions, devoting roughly half of Back to the Grindstone to Las Vegas-style funk and rap. Essentially, Milsap layers raspy vocals over a big, rousing chorus and lots of thumping bass a Nashville singer's hokey idea of modern soul. This ungodly cacophony reaches its nadir on ''Love Certified,'' a duet with Patti LaBelle, who takes one look at Milsap and declares, ''I can see you're hot to trot.'' It's a measure of LaBelle's talent that she gets through the song without breaking up. D

