Dan + Shay on Debuting New Song ’10,000 Hours’ at Justin Bieber and Hailey Baldwin’s Wedding

Country duo Dan + Shay were both on board with serving as impromptu wedding singers for their collaborator Justin Bieber last month.

Dan Smyers and Shay Mooney were guests at Bieber’s wedding to Hailey Baldwin in Bluffton, South Carolina, where they performed their new song “10,000 Hours” — which Bieber cowrote and lends vocals to — for the first time in front of a live audience.

“We had never rehearsed it,” Smyers told Entertainment Tonight at an event in Nashville on Wednesday. “We obviously recorded it in the studio, but we never played it live in front of actual human beings. [But] Justin was like, ‘Sing ‘10,000 hours,’ we’re like, ‘OK, we’ll try.’ “

Mooney joked the pair were “just making up the words,” Smyers adding: “It was good though, it was really fun and people were out on the dance floor rocking.”

RELATED: Justin Bieber & Hailey Baldwin Star in First Music Video Together for ‘10,000 Hours’ with Dan + Shay

Dan + Shay | Frazer Harrison/Getty
Dan + Shay | Frazer Harrison/Getty

The event marked the second time the Biebers married each other, first tying the knot more than a year ago at a N.Y.C. courthouse. To celebrate with friends and family, the happy couple opted to hold the larger ceremony on Sept. 30.

“It’s awesome to get to attend their wedding and it was a blast,” Smyers says. “It was a really good time.”

About 154 guests were in attendance, including Kendall and Kylie Jenner, Usher and Jaden Smith, a source previously confirmed to PEOPLE.

RELATED: Every Must-See Photo from Justin Bieber & Hailey Baldwin’s Star-Studded Southern Wedding

Also present was Dan + Shay’s and Bieber’s manager, Scooter Braun, who they say is responsible for making “10,000 Hours” happen by putting the three in touch.

“We’ve always wanted to do some collaboration with [Bieber] and we wrote the song and thought it would be perfect and sent it over to him not knowing what would happen,” Mooney told ET. “He loved the song; he’s in a similar place in his life, just got married, and so it was really cool to have that moment all together.”

Justin Bieber and Dan + Shay | Catherine Powell
Justin Bieber and Dan + Shay | Catherine Powell

Before the song was released, Bieber teased it by calling it “wedding music.” The lyrics feature the artists promising to love their significant other for “10,000 hours or the rest of my life.” In the song’s music video, Smyers, Mooney and Bieber are joined by their real-life partners, supplying idyllic visuals for an already romantic track.

RELATED VIDEO: Justin Bieber Made Wife Hailey Baldwin a Special Piece of Jewelry

“The timing of it worked out and we still can’t believe that it happened,” Mooney told ET. “I’m waiting to wake up tomorrow and [find out] like, ‘That actually never happened to you guys.’ “