Country music star Keith Urban revealed he was doing last-minute Christmas shopping when Taylor Swift asked him to appear on her re-recorded album.
Urban features on the Fearless (Taylor's Version) tracks We Were Happy and That's When.
Swift released the album, which originally arrived in 2008, last week as part of the process of re-recording her old material in a row over her master recordings.
Urban, who worked with Swift early in her career, revealed he listened to the new songs at an Australian shopping centre shortly before Christmas.
During an appearance on The Ellen DeGeneres Show, he said: "I'm at the shopping mall doing my Christmas shopping and I get a text from Taylor saying, 'I've got these couple of songs I'd like you to sing on, do you want to hear them?' and I said, 'Sure'.
"So she sends me these songs and I'm sitting in the food court at the shopping centre listening to these two unreleased Taylor Swift songs.
"It was an unusual place to be hearing unreleased Taylor Swift music but I love the songs and luckily got to put a vocal on both of those."
New Zealand-born Urban, 53, has two daughters with Hollywood actress wife Nicole Kidman, also 53, and told DeGeneres they are "big Taylor Swift fans", adding: "They were just excited dad got a text from Taylor Swift."
Fearless (Taylor's Version) includes previously unreleased tracks from the pop superstar.
It is on course to top the UK albums chart.