The Pistol Annies are one of two country groups invited to be a part of the Chieftains' 50th anniversary album. The Nashville trio will help the traditional Irish band celebrate on the T-Bone Burnett co-produced 'Voice of Ages,' scheduled for release on Feb. 21.

The announcement at Rolling Stone clears up the mystery behind a series of Pistol Annies' tweets from late October. “What an unbelievable experience. Thank you T-Bone," one Annie tweeted on Oct. 26. “Leaving the studio with the girls. 2nd day working on a lil treat with Tbone burnett .. Pretty sure I’m having a mini stroke. Too excited,” Ashley Monroe wrote on her personal Twitter page later that week.

Additionally, the Civil Wars have cut a song for the project. The Grammy nominated duo wrote and recorded the song 'Lily Love' for the album, and the Chieftains' Paddy Maloney couldn't be happier about it.

“In the ‘Lily Love’ melody, I can hear strains of the Irishness of it, and to play, arrange and add my thoughts to it just came naturally," he told Rolling Stone. Listeners can hear 'Lily Love' here.