Coldplay Debut New Song, Perform With Ariana Grande at Global Citizen

Global Festival curator Chris Martin also appears during Ed Sheeran's set to sing "Thinking Out Loud"

Chris Martin served as curator of this year's Global Citizen Festival in New York, so it was destined that the Coldplay singer had some big plans for the Central Park fest. Martin delivered threefold by bringing out unannounced guest Ariana Grande during Coldplay's set, making an appearance during Ed Sheeran's performance and debuting a new Coldplay song titled "Amazing Day."

Coldplay were the first band to perform Saturday at the Global Citizen Festival, and their set was immediately jeopardized by a piano that broke one minute before the band took the stage, Coldplay's official Twitter told fans. The broken piano forced Coldplay to remove "Clocks" and "Paradise" from their set list, but the group soldiered on and made amends for the shortened set by closing things out with a moving new ballad titled "Amazing Day," which the band rehearsed at their soundcheck the day before.

"And the view / the whole Milky Way / In your eyes / I'm drifting away," Martin tenderly croons on the new cut, which could be the first sampling fans have of Coldplay's upcoming (and possibly final) LP, tentatively titled A Head Full of Dreams. "And in your arms / I just want to sway / Amazing day."

Coldplay's broken piano also threatened the band's other big surprise: A surprise appearance by Ariana Grande, who joined the group to sing her Harry Styles-penned cut "Just a Little Bit of Your Heart." Martin and Grande rehearsed their duet on piano, which left Coldplay to improvise the performance on Saturday. It didn't matter as Grande and Coldplay combined for a compelling take on the My Everything track.

"Thanks @ArianaGrande for lighting up our stage. Your voice is a thing of wonder. Beautiful song by @Harry_Styles," Coldplay tweeted after the performance. However, Martin's day didn’t end with the Coldplay set as he appeared later in the festival during Ed Sheeran's set to join that singer on the X hit "Thinking Out Loud."

"When they asked me to play [Global Citizen], they asked me what song fitted in my sort of vibe, I wanted to play a song with someone who I'm a massive fan and admirer of, so I might as well bring him on stage," Sheeran said while introducing Martin. The two British singers got some practice for their duet earlier in the week when Martin stopped by Sheeran's Foxborough, Massachusetts concert Thursday to play "Thinking Out Loud" and Coldplay's "Yellow" with the X singer.

Rolling Stone spoke to Global Citizen co-founder Ryan Gall about Martin's 15-year role as the festival's curator, which kicked off with the 2015 fest. "[Martin] didn't want to do just a one-off. He wanted to sink his teeth into it and really do some meaningful work," Gall said. "He literally has called up artists. He called up Ed Sheeran personally. He called up Beyoncé personally. When we come up with an idea like, 'Hey, do you guys want to collaborate on a song?' it's just festival people trying to make it happen. But if Chris has an idea of collaborating and doing something unique during the performance, it's coming from the artist. It changes everything. "