DUBIOUS ACHIEVEMENT OF THE MONTH: "Intelligence borrows, but genius steals," Igor Stravinsky used to say, which makes the folks who edit the music department at Playboy magazine pretty smart cookies indeed. The magazine's July issue offers the debut of "Rockmeter," a new feature where a quintet of noted pop critics, using a scale of 1 to 10 (10, of course, being best) rate five new albums each month. (The critics, all East Coast-based, include Dave Marsh, Nelson George and Robert Christgau.) Rolling that title around on our tongue and gazing at the Rockmeter layout, which features five vertical columns with each critic's name at the top, we couldn't help but feel a little twinge of deja vu . To the untrained eye, it looks just like our regular Calendar feature, PopMeter. However, according to an introduction to the feature by Playboy's Barbara Nellis, we couldn't possibly have given the magazine the idea. She says: "Our incredibly hip record reviewers will be rating five albums on a scale of one to ten, just the way 'American Bandstand' taught us to do it." (Gee, we thought "Bandstanders" counted to 100.) Our only suggestion: If Playboy wants to be really hip, why not add a guest panelist each month? We've used everyone from Marshall Crenshaw to Molly Ringwald. Just give us a call--we'd be happy to supply their phone numbers.