Christina Aguilera hit the stage with A Great Big World on Tuesday's The Voice to sing their new ballad Say Something.
One of the two band members, Ian Axel, opened the performance playing and singing on the piano, while the second member, Chad Vaccarino, played the keyboard. Aguilera, who kept it casual in a T-shirt and beanie, chimed in as soon as the chorus started.
"And I will stumble and fall. I'm still learning to love, just starting to crawl," they sang. "Say something, I'm giving up on you. I'm sorry that I couldn't get to you. Anywhere, I would've followed you. Say something, I'm giving up on you."
After the performance, the band tweeted, "Oh my god. That was incredible. Thank you @xtina."
In a behind-the-scenes video released on Nov. 1, the two members expressed their shock that Aguilera wanted to be a part of their song.
"When our manager told us that Christina wanted to sing on one of the tracks, on Say Something, it was really hard to process," the band said.
Aguilera explained her desire to work with the group, whose album Is There Anybody Out There is hitting stores on Jan. 14, 2014.
"This song Say Something sort of is coming to me at a time when I'm feeling very inspired," she said in the clip. "I'm only taking on projects that feel good to me and represent as always a purpose of the here and now in my life and that's what this song Say Something actually does for me."