'The Voice' judge and pop star Christina Aguilera recently previewed tracks from her latest album, 'Lotus,' including a soaring, passionate ballad titled 'Just a Fool' with fellow reality show coach Blake Shelton.

"I did something with my favorite on the show, cause he's my big brother and I'm actually the closest to him of all the guys, is Blake," Aguilera said of Shelton during an album preview event. "He's just a rock star. He's great. He's so playful and so fun, and down-to-earth. He's got a great heart, which... I guess you see on the show."

Understandably, Shelton had a few challenges in making the duet, like fitting recording time into his already hectic schedule and the challenge of singing with the petite Aguilera, who has a powerful voice and astonishing vocal range. "He busted his a-- to make the time and God knows where he was," she reveals. "I got the e-mail after he heard [the vocals], because I was the first person to put my vocal down. He was like, 'I had to put a clothespin on my nutsack just to hit some of these notes. Why did you make it so high?' But that's good ole Blake, what's why I love him."

For several months, it has been rumored that Shelton might also collaborate with another coach from 'The Voice,' Cee Lo Green. “I have a song for Blake Shelton that I gave to him. And I’d like to do it alongside him,” Green told the Associated Press earlier this year. “I’d like for it to be a duet.”

No word on if the Green/Shelton duet has come to fruition.

Hear a Preview of Christina and Blake's 'Just a Fool' Duet

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