No one I know texts me at 6am. But my phone buzzed incessantly one Monday morning while I struggled with my coffee-maker.

“This is Matisyahu,” the message read. “How’s it going?” Clearly, this wasn’t going to be a typical celebrity interview.

Over the course of 25 more messages to sync our schedules — including one where he didn’t recall ever messaging me in the first place — I learned “Matisyahu likes to make his own arrangements,” as his PR delicately put it.

That might not work so well for logistics, and one hopes someone else is in charge of organising his upcoming European tour. But it’s turned out to be a huge asset creatively. Thirteen years after his debut as a shtreimel-wearing, Torah-toting reggae crooner, Matisyahu is indeed making his own arrangements. And with Undercurrent, his new, critically acclaimed album, the former Matthew Paul Miller is sounding a musical declaration of independence along with a deliberate, almost defiant spurning of trends.

His bio describes the new record as a “journey inward”. What does that mean, I ask when we finally manage to arrange our interview.

“It’s mainly through the listener,” an alert-sounding, good-humoured Matisyahu tells me from his home in Nyack, about 30 miles north of Manhattan. “All music is a journey inward. The concept of this record is currents that flow, under the surface, in different directions. They bring us back around in cycles. When I play it, people close their eyes and think into it. The tracks are long, and the music takes them on a journey.”

Undercurrent, he continues, is meant to capture his live performances, which — with a hand-picked new band — have evolved into jam sessions that make the Grateful Dead seem like The Ramones. I ask how his new output will translate in a social-media-driven music economy where big gestures and memes propel sales and downloads.

“It’s the complete opposite,” he shoots back. “While I’m into the notion of making music for YouTube, I’m really at the point of my life where it’s about making an organic record that captures what I do night after night.” With its loping energy, spontaneous flourishes, and restless melodies, Undercurrent comes close to doing that. “When you step into the unknown, your music starts to evolve and grow, and your sound really starts to develop,” Matisyahu says. “We recorded all of these improvisations from a year of touring. We got off the road, went into a tiny room in Brooklyn, chose the best ones, and recorded eight songs that are on the record, each eight or nine minutes long. It’s a whole conversation with the musicians. It makes these eight-minute songs feel like two minutes to me”. Undercurrent’s vinyl release, he notes wryly, is a double LP. “It feels like a throwback,” he says. “When I listen to it now, I go into my office, sit on a rug, and play the vinyl.”

Matisyahu circa 2017 — shirtless, clean-shaven, and pony-tailed in a video for new single Step Out Into the Light — is the latest iteration of a chameleon-like persona. When he broke out big with 2004’s Shake Out the Dust, he was a gangly 25-year-old in full Chasidic garb whose novelty fed his notoriety. In a 2010 interview with the JC, he had shed the black suit, but was still bearded with a kippah, and a tallit under his t-shirt.

The following year, Matisyahu made global headlines for shaving his beard: “akin to Tim McGraw taking off his cowboy hat,” opined the Washington Post. “No more Chasidic reggae superstar,” Matisyahu tweeted.

That, he says now, was the start of his transition from Matisyahu the person to Matisyahu the band. “It was the notion of coming off the mountain as this spiritual, isolated entity, to being in the real world with real people. I realised how important people are to me. Collaboration’s important to me. It’s not just about what I want.”

A troubled teen who ended up in rehab after high school in suburban New York, the college-age Matisyahu moved to Oregon to explore a music career, and built a small local following as a Jewish rapper. “It was open mics and college bars in the Northwest,” he says. But after returning home to resume his studies at New York University, he couldn’t find a band.

“I became a bit of a loner,” he recalls. “I spent a lot of time in my room listening to instrumental tapes. I smoked a lot of weed, wrote a lot of lyrics, and beatboxed. I wasn’t necessarily happy, but I was hungry. I wanted to do more. I was in a dark place, a little tortured. I had all this creativity but I wasn’t disciplined enough to manifest my dreams. And that’s when I got religion.”

Matisyahu embraced Judaism with the same fervour he had devoured music. “I turned to God, and surrendered everything,” he says. “Judaism became my quest. I moved to Crown Heights. I stopped music. I lived in a basement and studied Torah 24/7 for a year-and-a-half.” And then, he says — wonder still in his voice at the memory — “my career happened in this magical and mystical manifestation.”

Former college buddies turned music managers somehow tracked him down. They wanted him to become their first artist and start booking shows. “I had put down everything I wanted so I could look at what it was and whether it was right for me,” he recalls. “I knew I was talented. I knew I could inspire emotions with music. I knew it could come from my heart to another person. And in my moment of letting go of all that, karma threw it back at me.”

Matisyahu’s first headline show took place at Southpaw, a now-closed, 400-capacity bar in Brooklyn. “It was Chanukah. I walked up with a gemara in my hand,” he says. “I saw a line of people. And it hit me that the show was sold out.” After his next gig, a sold-out night at Manhattan’s hipster-cred Mercury Lounge, “I told my rabbi, ‘Dude, I can affect a lot more people if I can get this out there.’ I got permission to tour as long as I got married. I did, and got my then-wife pregnant. And I bought a van and hit the road.”

That journey launched a highly unconventional — but hugely successful — career that’s allowing Matisyahu circa 2017 to do things his own way.

“The audience is growing, and it’s really eclectic at this point,” he says. “I’m in one of those places where the music grows on its own. When someone’s introduced to Bob Marley or Sublime, they might get my record. Someone visiting Jerusalem might hear Jerusalem on a tour bus. One Day was used on The Voice in the Philippines.”

His new band is part of his declaration of independence. “A few years ago, I fired my manager,” he says. “I stripped my band back. I hired my dad to drive my van. We went on the road with no lights, no sound. Since then, we’ve gone back to full lights, production, and sound. And I’ve added one person at a time to the band. I spend more than 200 days a year on the road, and it has to be with people I love unconditionally.

“We’ll pull into a city in the early morning. Depending on how late I was up the night before, I’ll wake up later in the day. As singer, the most important thing is sleep, so I try to sleep as much as I can to save up energy. But if we’re promoting a record, I might be up at 7am, and the crew will be loading gear at a radio or TV station before moving on to set up at the venue. I’ll get on the phone for interviews, email, phone calls, my managers and agents. It can be crazy stressful, or super-healthful — and right now, I’m cooking macrobiotic food, doing yoga, running, and super-on-point healthy.”

When he’s not on tour, Matisyahu is with his three sons at his sprawling riverfront house in Nyack, 30 miles north of Manhattan. “I’m making it an artists’ retreat and arts incubation centre. I want to see people recording and painting here,” he says. A group of former yeshiva bochers are his first endeavour.

“They were all put in one yeshiva, and they formed a band listening to my music,” he says. One of the boys is the youngest of 10, and his parents hosted Matisyahu early in his touring career. Now, “the kid plays drums. He’s also the house engineer. He had his friends come over to jam the other night, and they’re freaking sick. They’re the sickest musicians I’ve heard in a long time.” He’s hoping to help shape their nascent career as a band.

“That’s the thing I’m really interested in doing right now — to help birth the next thing,” he says. But I’m an artist that has to tour to keep everything afloat.”

A memoir, King Without a Crown, is due this year. A comic book he co-wrote accompanies Undercurrent’s release. And a Matisyahu biopic has started production; Kevin Asch, who helmed the Jesse Eisenberg vehicle Holy Rollers, will direct.

Tickets have just gone on sale for his extensive late-2017 European tour, including a London date on September 11.

“I have so much going on right now. But I’ll never compromise on making music,” he says. “I’ll always be pushing myself. And I’ll always grow.”