As he worked on his new album, the blues rocker Ben Harper looked on with horror at the killings of young African Americans and knew he had to put their plight into song.

"I have to write about what moves me the deepest or what's knocking the loudest. I wanted to say it loud," said Harper, whose 13th studio album, "Call It What It Is," comes out Friday.

"There was Trayvon Martin, Ezell Ford, Michael Brown," he said, referring to unarmed African Americans who have been shot dead, with Brown's 2014 killing by police in Ferguson, Missouri setting off mass protests.

"By the time it got to Michael Brown, it was my tipping point. My back was against the wall," Harper told AFP on a recent visit to Paris.

Harper on the album's bluesy title track concludes with the line, "Call it what it is -- murder."

Activism is not new for Harper, whose early successes included the 1994 song "Like a King" about Rodney King, the African American motorist whose filmed beating by white Los Angeles police set off riots after the officers were acquitted.

Harper noted that the latest killings took place under Barack Obama, the first US president who is African American, and said that race was inadequately discussed in the United States.

"I do think possibly having a black president, it made it a lot better. He's such a symbol around the world, a cultural symbol," he said.

"But I also think that it stirred things up from the bottom. There's been too many situations now to not look at race, culture and politics holistically and question, why now?

"People are so used to pressing the delete button and making things go away quickly that they think that culturally the same thing will happen, but there is no cultural delete button, right?"


Morning coffee and slide guitar

Besides his return to activism, "Call It What It Is" marks Harper's reunion with his old band, the Innocent Criminals, for the first time in eight years.

"You have to know in your life when it's time to make the right moves, you hope. It had been too long. All roads led back to my original band," he said.

Harper has stepped up collaborations in recent years, forming the rock group Relentless7 and the more folksy Fistful of Mercy. He has also recorded with the blues harmonica player Charlie Musselwhite and his own mother Ellen, who runs the Folk Music Center in Claremont, California.

"The way our voices sound together is like I could never sound like that with anyone else 'cause it's my mom.

"Same with the Innocent Criminals, I've been with them in the 90s, 2000s and 2010s. We've known each other so long that there is a sort of genetic encoding," he said.

On the new album, the band revives its blues rock with Harper taking the lead on slide guitar. Harper and the Innocent Criminals go to a more rugged sound on "When Sex Was Dirty" and bring in reggae elements on "Finding Our Way" while also producing powerful ballads "Deeper and Deeper," "All That Has Grown" and "Goodbye to You."

But not all of the album is stern, with the chorus of "Pink Balloon" inspired by his daughters.

The reunited band plans an extensive tour for "Call It Like It Is," with dates until the end of the year throughout North America and Europe as well as dates in Australia and New Zealand and Japan's Fuji Rock Festival.

At 46, Harper said he no longer felt obliged to write one song each day as was long his habit. But he said he cannot imagine spending a day without creating music.

He wrote "Call It Like It Is" quickly but said that he is content simply to jot down a few lines before the end of a day.

"When I wake up in the morning, I pick up a slide guitar. That's the first thing: coffee and slide guitar," he said.

"I don't force a song a day, I let it come."