"Rigamortis" is one of the standout songs on young, verbose L.A. rapper Kendrick Lamar's great Section.80 album. It's a blistering double-time technical workout over a floating early-'90s-style jazz-rap horn loop. And now it has the video it deserves, in which Kendrick, backed by a drummer and a couple of horn players, runs his mouth in an art museum and on ...