Country duo Dan + Shay will be adding their expertise to the new season of The Voice U.S.

The duo has signed on to serve as advisors to Shelton for his 20th season on the show.

"The way they (Dan + Shay) come together and vocalise together and make music, I thought that would be a great mentor to have, these two, because so many times I'm sitting here in a situation with these battle rehearsals and one of the artists will ask me a question about harmony, and I don't know c**p about harmony," Shelton told Access on Monday. "I'll be like, 'Oh, you know, I'm gonna check on that for you', and then I never do, because I don't know anything about harmony.

"Finally, this season, I've got Dan + Shay here, who, you know, they kill it. And they're a natural at it, and honestly, it's already come into play a couple of times. It's helpful to have them here."

The duo was happy to join Team Blake after Shelton became the very first major country artist to take them on the road.

"He took us out on literally our first tour, the Ten Times Crazier Tour, and I don't even think we had a hit on the radio at that point," Dan Smyers recalled. "He took a chance on us and we became super close out there. Blake, as successful as he is, is the most humble, down-to-earth dude out there and just an incredible person, and incredible role model. We learned so much from him."

Season 20 of The Voice kicks off on 1 March, with Shelton up against Kelly Clarkson, John Legend, and Nick Jonas.

Luis Fonsi will advise Clarkson, while Glee star Darren Criss and Brandy will serve as advisors to Jonas and Legend, respectively.