Blake Shelton surprised fans with a special duet during his Friends & Heroes Tour date in Denver, Colorado at Ball Arena on Friday (Aug. 20).

The country superstar was joined by his longtime friend and fellow coach on NBC’s The Voice, Kelly Clarkson, for a duet of “Lonely Tonight,” a song that originally features Pistol Annies’ Ashley Monroe.

Clarkson, who labeled Shelton the ‘Prince Of Country,’ joined Shelton on stage mid-show for the memorable moment where the superstar pair traded vocals and flawlessly harmonized to the popular tune.

“Kelly freakin’ Clarkson Denver,” Shelton gushed as their performance concluded and Clarkson added, “give it up for Blake Shelton.”

Co-written by Brent Anderson and Ryan Hurd, “Lonely Tonight” appears as the second single on Shelton’s eighth studio album, Bringing Back The Sunshine (2014). The song went on to receive a GRAMMY-award nomination for Best Country Duo/Group Performance.

Watch their performance in the below fan-captured clips.

“Seein’ my brother from another mother tonight y’all!! Blake Shelton is bringing the honky tonk to Denver!! MAMA. IS. HERE. FOR. THE. PARTY.” Clarkson shared in her Instagram story ahead of their performance.

Clarkson continued to gush over the acts appearing on the bill, including Tracy Byrd and Martina McBride. She even shared her favorite part of Shelton’s show, which she admitted would have her childhood self freaking out.

“My favorite part of Blake Shelton’s show tonight was the song circle acoustic vibe!! My childhood self is losing her mind!!” Clarkson added.

She later added, “Blake Shelton is KILLIN’ IT tonight in Denver!!! I’ll give him this #PrinceOfCountry. His setlist is INCREDIBLE!!”

“Get it @blakeshelton we are LIVIN’ OUR BEST LIVES!!! THANK YOU ,” Clarkson captioned a photo of her and her friends at the Shelton concert.

Additionally, Shelton and Clarkson are both set to return to their red chair on NBC’s The Voice in just 4 weeks alongside Ariana Grande and John Legend.