The odd couple has recorded E Piu Ti Penso, originally composed by Ennio Morricone for Sergio Leone's 1984 crime epic Once Upon a Time In America, for opera star Bocelli's upcoming album, Cinema, which is dedicated to songs from the big screen.

Ariana, who is of Italian descent, shared a link to the track on on Saturday (26Sep15) and revealed the duet was a dream come true.

"So honored to be on this song with you, Andrea!," she tweeted. "you don't know what it means to me & my family! mille graze (sic) (a million thanks)! baci (kisses)!!!"

The collaboration debuted hours before the singer joined Coldplay onstage at the Global Citizen Festival in New York City on Saturday for a surprise performance. Ariana was invited to belt out Just A Little Bit Of Your Heart with the British rockers, sharing vocals with frontman Chris Martin.

She later expressed her gratitude to the band online, writing, "thank you @coldplay it was an honor to say the least", while Coldplay revealed the feeling was mutual, adding, "Thanks @ArianaGrande for lighting up our stage. Your voice is a thing of wonder".

Ariana and Martin weren't the only unexpected duet partners to grace the stage at the Global Citizen Festival. Rapper Common introduced Sting to perform Every Breath You Take and One World, Beyonce joined forces with Ed Sheeran for Drunk In Love, and the R&B superstar later teamed up with Pearl Jam for a cover of Bob Marley's Redemption Song.