Paul McCartney and Neil Young are a smart couple of fellas, and they understand basic universal laws. They get that the already formidable appeal of one boomer rocker is compounded into something particularly, chemically, monstrously irresistible when two boomer rockers take the stage. And so, gathered at “Oldchella,” an event specially primed for fans to frenzy, McCartney and Young didn’t just leave their loyal patrons content with separate sets. No, Young joined McCartney, and the two teamed up for “A Day in the Life,” “Give Peace a Chance” (both above), and “Why Don’t We Do It in the Road” (below), the latter of which gave way for a properly bangin’ Neil Young guitar solo. This is the wisdom of fathers, children; they know of what they rock.