Barry Gibb was "terrified" when he heard his collaborator Keith Urban would be bringing his wife Nicole Kidman to the studio.
The Bee Gees star was thrilled when Keith agreed to join him for a new rendition of I've Gotta Get a Message to You for the country duets album, Greenfields: The Gibb Brothers Songbook Vol. 1, but had no idea he'd be joined by the Oscar winner.
"He gave us a great gift because he brought Nicole with him, and that was such a thrill," Barry told Billboard. "I'm freaking out, you know."
Barry also re-teamed with Dolly Parton, who recorded his Islands in the Stream song as a duet with Kenny Rogers 40 years ago, revealing he had never met her since.
"Dolly was a great thrill, and as incredible as she always is," he added. "She's such a humble person. I just don't understand how people of that stature remain calm and humble and ready to have a laugh, you know?
"Dolly told me that where she was standing at the microphone (at Nashville's legendary RCA Studios) is exactly where she stood when she did I Will Always Love You and Jolene. You know, that's mind blowing."
And Barry also really enjoyed working with Olivia Newton-John, who was "spot on from the first note".
"She hasn't been in the studio for awhile, she'd been out of action, and she was so thrilled to just get back to singing," he recalled.