You could be forgiven for thinking that any and all modern articulations of “rock music” have become politically toothless. As a medium, it doesn’t quite seem as suited to critiques of society and culture as it once did. That being said, it seems Detroit four-piece Protomartyr would be inclined to disagree. Relatives In Descent, their fourth album, finds them wrestling with the nature and form of truth, spurred on by the vertiginous, collective sense of History swarming violently around the present. Having recently signed to UK Label Domino, the band retreated to L.A. in March of this year to record…