GLEE: Jonathan Groff interview on returning to GLEE

Before Glee, Jonathan Groff would have not been able to sing Adele's guttural, smoldering anthem of heartbreak, "Rolling in the Deep," which he used to swagger back onto the hit show last week. The actor, previously best known for his work in New York theatre, says it was Glee that taught him to rock out.

"The first song I sang with Vocal Adrenaline was 'Highway to Hell' and I remember calling [music producer] Adam Anders and saying, 'Maybe we should sit down with a piano instead because I don't sing like this,'" Groff tells TVGuide.com. "But he pulled out this side of my voice I didn't know existed, this rock scream. It has totally changed the way I sing."

It was that rock edge that accompanied the return of Groff's Jesse St. James. A year ago, the devious show choir wonderboy made Rachel swoon to Lionel Richie's tender come-on "Hello," but since then he broke her heart, and deprived New Directions of a victory — so only Adele's pissed-off, breakup-mourning duet would do. Still, the 26-year-old actor says going back to Glee was as much of a surprise to him as it might have been to viewers who remember the cruel way his character ended things with Rachel: Right before leading Vocal Adrenaline through a title-clinching rendition of "Bohemian Rhapsody," Jesse revealed his true colors, smashing an egg on Rachel's head and dumping her.

"Totally harsh," Groff says. "I remember reading the script and being like, 'Oh my God, that just happened. Okaaaay.'"

But having convinced Rachel in Tuesday's episode that he was a changed man — now a college drop-out with glee club still on the brain — he's returned to McKinley High to help coach New Directions before Nationals, and possibly woo back Rachel. (Don't bother asking if his plan works, Groff's not telling. Also, he adds, "I just finished my first day of shooting. I've sung one song with Lea, so I also honestly don't know," he says.)

In any case, the offer to reprise Jesse couldn't have happened at a better time. Groff has kept busy since his last appearance, making his West End debut in a production of Ira Levin's Deathtrap, but he'd been contemplating a move from New York to Los Angeles to pursue more film and television roles. His resume, while short, boasts being cast by Ang Lee as charismatic concert promoter Michael Lang in 2009's Taking Woodstock and Robert Redford in this year's Civil War-era thriller The Conspirator.

Fortunately while he worked in the UK, he kept up with Glee's second season via iTunes. "Because I love it, not because I thought I'd necessarily be back," he says.

"Glee had been the longest job I'd ever done in front of the camera, and I really enjoyed it," Groff continues. "It felt like it was time to take a risk and move out here to L.A., try and get some film and television going. I'm still keeping my place in New York because I couldn't bear to give it up, and I love doing theater."

(Read more on TVGuide.com)