(photo: Sonny McCartney / MPL Communications) For an artist who’s spent the better part of six decades rewriting the rules of pop music, Paul McCartney has somehow managed a genuine first: a full-fledged duet with his Beatles bandmate Ringo Starr. The nearly 84-year-old McCartney unveiled the track, titled “Home to Us,” today (May 5) during an intimate playback event at London’s Abbey Road Studios, where 50 fans were invited inside the legendary Studio Two for an early listen to his May 29 MPL/Capitol album The Boys of Dungeon Lane . The song drops Friday (May 8) as the second preview of the record, following the warmly received “Days We Left Behind.” As previously reported , The Boys of Dungeon Lane finds McCartney in an unusually introspective mode, revisiting his Liverpool childhood and the pre-Beatles years with a level of detail and emotional openness that sets it apart from much of his recent work. “Home to Us” appears to sit right at the center of that concept both thematically and historically.…