“It’s up on Bowery and Rivington—the old Pioneer Bar,” I instructed a friend on my cell, while looking curiously around the 3,000-square-foot space at 218 Bowery, which has recently been rechristened R Bar. The brand-new theme here is rock ‘n’ roll, or as the bar’s preview website states, “Rock n Roll Reinvent Reborn Revolutionary Renaissance . . . Is Coming.” What came is bordello-red walls, chandeliers, black padded walls, and stripper poles in the back, and a soundtrack curated by Billy Caldwell of Madchester’s late great Hacienda. It is Caldwell’s roster of unassailable tunes (Stones to Nirvana to Pixies) that’s the real rock star of this joint, that and the accommodating bartenders without any all-hail-keeper-of-the-booze ego trip. “I can make you anything,” our boy amiably announced, stirring up a solid Manhattan ($10) for me and not wincing when my lady friend asked for a lady drink, tequila with grapefruit ($8). Such kindly gestures almost make up for the schlocky black-and-white 3-D images of nekkid chicks straddling guitars behind the bar, or the high-school-level paintings of Debbie Harry, Iggy, and Mick. On that note, the owners needn’t have tried so hard. First lesson in rock ‘n’ roll: The real thing sells itself.