By James Sullivan – The Boston Globe, September 8, 2022

When Robert Plant sang those lines about having his lemon squeezed more than 50 years ago, he was drawing straight from the legend of Robert Johnson. Both with Led Zeppelin and over the four decades of his solo career, the Englishman whom many consider to be the archetypal voice of rock music has always welcomed the voices of ghosts.

So when he dropped by an LA-area record store recently and the owner mentioned he had a rare 78 RPM recording by Johnson stashed in the back, Plant had to restrain himself.“I didn’t blink,” he says, speaking from a tour bus in Oregon alongside his current co-headliner, Alison Krauss. “I didn’t let him see the lust inside me.” He laughs.In truth, the physical artifact does mean less to Plant than the mystery of the man who recorded it: “I am a record collector, but more so I’m looking for songs.”Plant and Krauss, who arrive in Boston to play the Leader Bank Pavilion on Friday, are revisiting their surprise, multiple Grammy-winning collaboration of “Raising Sand” (2007). “Raise the Roof,” which came out last November, finds the unlikely duo once again claiming a heterogeneous mix of folk, soul, country – and yes, old blues – songs as their own.

If Plant’s mutual admiration society with the bluegrass ambassador Krauss still seems unusual, they clearly share the dogged pursuit of great songs. They first came together in 2004, when Plant asked Krauss to accompany him at a tribute to Lead Belly at the Rock and Roll Hall of Fame. “We met for the first time in an Armenian dance hall where we were doing the rehearsals,” Krauss recalls. “I thought I recognized his head.” “Because it was still attached to my shoulders,” Plant interjects. They have a giggly camaraderie.Krauss, who famously signed with Rounder Records at age 14 in the mid-1980s, has grown up to be one of the most decorated performers in any genre. She was the woman with the most Grammy Awards until Beyoncé overtook her last year.From the beginning, theirs was an equal partnership.

“I don’t think I was for a minute thinking, ‘Come and do this for me,’ ” Plant says. “I have unfathomable depths of respect and care for Alison. I knew that was one of the most important elements – that we are absolute, total partners, coming from different ends of the deal. Nobody’s playing for anybody. We’re playing together.”

What drove them on the sessions for these albums was the challenge of stepping outside their respective comfort zones. For Krauss, it was engaging with music – “Trouble With My Lover,” a funky New Orleans tune written by Allen Toussaint for soul singer Betty Harris, or “Go Your Way” by Anne Briggs, a quiet figure from the British folk revival of the early 1970s – that she wasn’t familiar with. “I was really scared,” she says.

For Plant, it was finding the bluegrass-style harmonies that Krauss lives inside. They come less naturally to him; the American country music tradition “seems like the procreation of harmonies,” he says. “Both of us were probably looking for something slightly challenging. I think I use that word a lot.” These albums have required a good deal of preparation to make, he says. “You can’t just turn up and start singing ‘Baby, baby.’ ”

As with “Raising Sand,” “Raise the Roof” is produced by the estimable T Bone Burnett. Guests on the album include guitarists Bill Frisell, Marc Ribot, Buddy Miller, and David Hidalgo of Los Lobos. Opening act JD McPherson has been sitting in with the band on tour. It was drummer Jay Bellerose – “the driving wheel,” Plant says, who tipped the singer about that record store in LA. Krauss’s brother Viktor, who plays upright bass, is also part of the touring ensemble.

Krauss, who is 51, says she and Viktor actually discovered Plant’s music through his first few solo albums, with the MTV-era singles “Big Log” and “In the Mood.” “My brother and I were really taken with that stuff – so beautiful and mysterious,” she says. Only then did they reach back and begin to explore the Zeppelin catalog.

Plant, 74, has been looking back on certain songs from his career in music for the past few years on a podcast called “Digging Deep with Robert Plant.” He’s not averse to revisiting his work with the band that made him a hard-rock monument. “Everything’s relevant,” he says. “Everything has its time and its place. Sometimes I get full of magnificent emotion, brought to tears listening to stuff that I was a partner in way back.”

As an example, he mentions “Achilles Last Stand,” the 10-minute album opener from 1976′s “Presence,” which was recorded while Plant spent months using a wheelchair after a bad car accident.“That’s one that gets me, ‘cause I know what pain I was in then. I couldn’t even bathe myself. … Or the elation of something like [1969′s] ‘Good Times Bad Times,’ ” which was written when he was 20. “It’s pretty lewd, some of it, but it’s a long time ago.” At this age, he jokes, he’s “looking for clemency” for some of his youthful escapades.

Mostly, though, he’s focused on the current work.

“It’s like Donovan said – ‘What’s Bin Did and What’s Bin Hid.’ It doesn’t matter. You only live what you’re doing in the present tense. That’s how I see it.”