A hard touring troubadour, Ben Harper has brought his message of love and hope and his amalgamation of styles — folk, blues, R&B, reggae, soul, and even pop — to diverse audiences the world over. Both Sides of the Gun is an 18-song collection, deliberately divided into two separate moods. The first half is reflective, featuring somber ballads and dream-like instrumental passages (“Sweet Nothing Serenade”) where vibes and his slide acoustic-guitar playing loosely gaze the day away. Listen closely and you hear a man aching to connect with a peace he doesn’t find in the world. “Reason to Mourn” is shadowed by a sad-core orchestration and eventually the modest joy of a psychedelic guitar solo. For the second half, Harper turns on the electricity and his rage over the day’s current events — Hurricane Katrina, the war in Iraq — spills over from the lyrics (“Black Rain,” “Gather ‘Round the Stone”) to the impassioned playing that often recalls the soulful funk of Curtis Mayfield and the Rod Stewart-led Faces in their rag-tag glory (“Engraved Invitation”). Harper’s sense of adventurism serves him well.