Continuing their slow crawl toward middle age, Linkin Park opt for moody over metallic on A Thousand Suns, their fifth album. A clear continuation of 2007’s Minutes to Midnight, A Thousand Suns also trades aggression for contemplation, burying the guitars under washes of chilly synthesizers -- a sound suited for a rap-metal band that no longer plays metal but hasn’t shaken off the angst, choosing to channel inward instead of outward. So few rap-metal bands have chosen to embrace their age that it’s easy to admire Linkin Park’s decision not to shy away from it, even if their mega-success gives them the luxury to pursue musical risks. The subdued rhythms, riffs, and raps of A Thousand Suns maintain a brooding mood.