Singer Undergoing Renovation

His living room had been commandeered by a pair of assistants, one pecking at a laptop and the other mulling over wardrobe options for a scheduled tour. Apologizing for the lack of a couch, Mr. Groban offered a seat in one of two squat wooden chairs — gifts from the West African singer Angélique Kidjo — while he gathered Sweeney, his wheaten terrier, for a walk in the park.

The move to New York has capped a series of pivotal shifts for Mr. Groban since his last studio effort, “Noël” (Reprise), sold 3.7 million copies in less than three months, making it the top-selling album released in 2007. (That figure has now reached five million.) He changed his management and began to explore his options in the wake of a failed relationship with the actress January Jones. And after working for nearly a decade with the heavy-pomp producer David Foster, who discovered him as a teenager, he made his new album, “Illuminations” (143/Reprise), with Rick Rubin, the high priest of strip-it-down.

It all amounts to a top-to-bottom renovation of one of the most stable operations in the music business, with a mostly older, mostly female fan base (Oprah Winfrey is a big fan) and more than 20 million albums sold.

“I really left behind every safety blanket I had,” he said. “I had just come off the heels of the No. 1 record of the year, and I can’t count how many times somebody came up to me and said, ‘Oh, are you going to make another Christmas record?’ You think to yourself just how easy that would be to keep recording Groban does this, Groban does that.” And there might be a time in his life, he added, where he would “feel perfectly comfortable” with that. “But for better or for worse, there’s still some fire and some exploration in me. I felt like it was a natural progression for me to start making it a little more personal.”

Intimacy and grandeur are hardly opposites in the world of Mr. Groban, 29, who was once memorably pegged (by Stephen Holden in The New York Times) as “our national choirboy.” But many of the songs on his previous albums offer the equivalent of a love note etched in skywriting, suitable for ceremonial purposes. “Illuminations,” which showcases Mr. Groban’s songwriting, reflects the conviction that gallantry can also be pensive and uncertain.

On the surface Mr. Rubin, best known for his work with the Beastie Boys, Metallica and late-period Johnny Cash, would seem an unlikely fit. But Mr. Groban was a fan. “You don’t hear a stamp so much, like you do with other producers,” he said of albums produced by Mr. Rubin. “You hear the most honest, organic representation of that particular genre and artist.”

The admiration was mutual. For Mr. Rubin the collaboration posed a challenge: “My goal was to make an album that was different than all the albums he made before and that would be the favorite album of people who love him. I also wanted it to be the album that people who didn’t like him would like.”

When it comes to his wholesome image, Mr. Groban is definitely in on the joke. An avid karaokegoer and a deft mimic, he has put in cheeky cameos on “Glee,” a series that embraces what he fondly calls “big singing.” In a video recently posted to the Web site Funny or Die he plays his own hapless interviewer. (“My mom’s a big fan, by the way.”) And in “Crazy, Stupid, Love,” a coming movie starring Emma Stone and Steve Carell, he plays a caddish lawyer — the humor arising partly from the sheer implausibility of such a thing.

Behind the self-deprecation, though, is someone acutely aware of outside perceptions. “All of a sudden when success hit, you get demos from publishing companies, and you wind up saying: ‘Is this how they view me? Is this what they think I am?’ And you realize: ‘Well, yeah, if you don’t do anything about it, you’re just going to get a bunch of songs like this.’ ” The urge to write, he said, “started with hearing things I didn’t want to sing.”

He had dabbled in songwriting on previous albums, working with a range of partners, from the new-age cosmopolitan Eric Mouquet to the art-pop technocrat Imogen Heap. What he had been missing was a sense of continuity and the comfort to dig in deep. Mr. Rubin connected him with Dan Wilson, the lead singer of Semisonic, and a Grammy Award winner for his work on the Dixie Chicks’ 2006 album “Taking the Long Way.” Mr. Rubin thought that his sensitive lyric writing would work well with Mr. Groban’s sweeping melodic sense.

Mr. Wilson came to the table with an understanding of his task. He recalled: “I told Josh: ‘We need a room with a high ceiling and a grand piano and a big window. And the only place we’re going to find something like that is in Minneapolis, at my house.’ ”

Mr. Groban took him up on the offer, and they quickly hit a stride, writing “Higher Window,” a song of romantic reckoning, in a day or two. At one point, facing an impasse, Mr. Wilson posed the question: What would Neil Diamond do? “And Josh basically sang about four lines in a row, off the top of his head, in Neil Diamond’s exact voice,” he said. “Some of those lines were funny, but some were awesome.” (Or both, perhaps: “Here I am, the one-man band/With a song that’s meant for two.”)

Mr. Groban and Mr. Wilson met in Minneapolis every few months, sharing their results with Mr. Rubin, who had clear ideas about what worked. (The words “singer-songwriter” were “a no-no to him,” Mr. Groban said, as was any hint of blues inflection.)