Not even a surprise concert by Blake Shelton could stop traffic in New York City Thursday night.

The country singer and “The Voice” judge made an unexpected appearance in Greeley Square, across from the J.C. Penney Manhattan store, in his role as the company’s JCP Cares ambassador. Shelton sang a couple of holiday tunes from his new Christmas album, backed by a USO Show Troupe. He joked that the singers were so talented that he’d like them to join his tour in the future. “Do you travel?” he asked.

A couple of times, Shelton had to sing over the jarring sounds of fire engines attempting to get through the packed streets. But he took it in stride, smiling widely in the middle of his set and saying with a shrug and a wave of his hand, “It’s New York City!”

Shelton, who is the reigning Male Vocalist of the Year of the Country Music Association, is gearing up for the Grammy Awards on Jan. 26, where he’s nominated for two awards. He’ll also join Merle Haggard, Willie Nelson and Kris Kristofferson for a number, a daunting task he said he views as “a bigger deal than winning one.” Kristofferson is receiving a Lifetime Achievement Award.

Before taking the stage, Shelton talked a bit about his holiday plans, saying he and wife Miranda Lambert plan to visit her hometown in Texas before heading back to Oklahoma to visit his family. “I actually look forward to it all year long,” he said. “It’s just no pressure, no thinking, just hanging out and having fun.” Lambert was backstage during the pop-up concert, but pulled up the hood on her coat and stayed out of sight of the crowd that gathered to see the performance.

The event, which included a 3-D projection of holiday animation and virtual carolers on the outside of the Penney’s store, also served to publicize the company’s Join the Jingle campaign. Penney’s will donate $20 to anyone who submits a video of themselves singing “Jingle Bells” on its Web site through Dec. 31. So far, more than $1 million has been raised for the USO, the company’s charity partner this year.

Debra Berman, Penney’s chief marketing officer, said Shelton and his well-publicized support of the troops make him “an amazing partner.” She also said that after the Penney’s stores close on Christmas Eve, the retailer will unveil a commercial with Shelton singing “Silent Night” with USO families in the background that will be “a real tearjerker.”