Getting into the studio and writing a potential hit song for Adele sounds hard enough. Now add keeping mum about the track for a year.

That’s the challenge Greg Kurstin faced after producing and co-writing “Hello” last year.

“I’m not going to lie; it’s not easy to hold that information in for that long. It’s kind of like I was holding this big secret for so long, but I stuck with it,” the Grammy and Golden Globe-nominated songwriter-producer, said in an interview with The Associated Press.

“It wasn’t easy. You kind of want to shout it out, run around in the streets yelling to random strangers what you’ve just done,” he added.

Just two weeks old, “Hello” has topped the iTunes singles chart in 85 countries. The music video broke the Vevo record for most views in a day with 27.7 million.

“Hello” is Adele’s first single since releasing 2011’s earth shattering “21,” her sophomore album that sold more than 11 million units in the United States and won the Grammy Award for album of the year, among other accolades.

“I’m still in shock honestly. ...I was just pretty blown away,” Kurstin said of the insta-success of “Hello.”

Kurstin, who has worked with Pink, Lily Allen, Katy Perry and Taylor Swift, said he and Adele were supposed to work on music for “21,” but that it didn’t pan out. On “25,” which Adele will release on Nov. 20, he also contributes to the tracks “Water Under the Bridge” and “Million Years Ago.”

Kurstin said he was putting some pressure on himself before meeting with powerhouse singer since this was her follow-up to “21.” But that changed once he set foot in the studio, and they started working on songs last year, including “Hello.”

“She’s just so wonderful to be around. She is funny and she’s just so down-to-earth. ...You can immediately relate to her and connect with her,” Kurstin said of Adele. “I really felt very comfortable around her because she makes you feel that way. She’s just cool, and then she gets on the microphone and of course blows your mind.”