Harper has a wide range, and he fires away

Ben Harper is an artist aflame with the possibilities of rock and soul, a restless singer-guitarist tangled up in the lineage of folk, blues and roots reggae. He has the chops to have been a guitar hero above all else, all about technique and sonic pyrotechnics, but by choice he’s a songwriter first, with an agenda both personal and political.

That message was delivered for more than two hours Friday at the Greek Theatre in a performance that offered endless comfort and outrage to a full house in the first of two nights at the venue. Those fans represented a hidden constituency of true believers, who have discovered Harper’s vivid blend of classic pop music styles despite little radio airplay and uneven critical support.

Their reward was a concert with the ambition of a major rock artist, suggesting the hand of a Springsteen or a Petty at work. If nothing else, Harper is an old-school rock classicist, committed to content over commerce, and one who hasn’t yet sold his music and image to the likes of the Gap or Victoria’s Secret.

Instead, Harper unfolded a world of darkness and rage on “Black Rain,” a brooding rocker on the drowning of New Orleans and government failure to respond: “You left them swimming for their lives!” He soon sat down with a lap slide guitar to ignite his early signature song “Ground On Down,” slapping and bending the strings to create a storm of excited gutbucket blues.

On “Glory and Consequence,” Harper sang with the sharp, desperate voice of a classic soul shouter. Just as powerful were his moments alone onstage, from the delicate “Morning Yearning” to the mournful, hopeful “Waiting for You,” which had a bit of acoustic Ziggy Stardust within the song’s crisp, emotional chord patterns.

No one coasted in his band, the Innocent Criminals. Bassist Juan Nelson was again a central force, and each player propelled the songs without colliding into one another, keeping the complex arrangement of overlapping sounds on “Forgiven” from crashing down.

If there has been one recurring complaint from critics of his eight studio albums, it is that Harper’s range has sometimes meant a crowding of styles from one song to the next. His 2004 collaboration with the Blind Boys of Alabama, the Grammy-winning all-gospel album “There Will Be a Light,” escaped that verdict. And his newest, “Both Sides of the Gun,” wisely splits the album into two dynamic discs: one quiet and acoustic, the other louder, angrier.

During his encore set, he was joined by support act Damian “Jr. Gong” Marley for a round of “Exodus,” which was dropped right in the middle of Harper’s “Jah Work.” Harper and the youngest son of reggae icon Bob Marley had an easy rapport, sharing a weakness for joyous harmonies and organic audience participation.

Marley’s earlier set blended the generations of reggae, mingling roots with dancehall, weaving “My Name Is Junior Gong” into his father’s classic “Crazy Baldheads.” Like Harper, Marley is a modern artist deeply aware of the past while focused on the possibilities of the present.