It wasn’t until the final song before the encore at WMZQ Fest at Jiffy Lube Live that country trio Lady Antebellum revealed the “huge surprise” the group teased on social media ahead of Saturday’s show. It was a doozy. Thirty members of George Mason’s “Green Machine” pep band, along with Dr. Michael Nickens (a.k.a. Doc Nix) and associate director Jeremy Freer, helped Lady Antebellum perform their hit single “You Look Good.”

“It was amazing,” said Freer, who helped arrange the opportunity and handled all of the logistics for the collaboration.

The music for the show wasn’t finalized until late last week, so the Green Machine’s rehearsing was limited to a brief discussion in the parking lot before leaving for Jiffy Lube Live and the preshow sound check with Lady Antebellum.

“That was basically our trial by fire,” Freer said. “I have great confidence in the musical abilities of the students in the Green Machine. Their attitude and their ability is just outstanding, so I wasn’t worried at all.”

During the school year, the Green Machine features more than 200 members. About 50 members expressed interest in performing on Saturday and Freer selected 30 based on the instrumentation required for “You Look Good.” Freer filled out the drum line by playing bass drum for the first time, while Nickens played the baritone.

“We throw a lot of music at that band,” said Nickens, a music professor who has directed the Green Machine since 2006. “What we do throughout the year, at basketball games and other events, it really got us prepared for this. Our members are flexible, they can jump on something new with a great attitude, get themselves up to speed and help each other perform better. On top of the music itself, just getting into the spirit of a performance, they know how to work a crowd. My favorite part of watching the video is seeing my members run out on the stage and they’re immediately reaching down and giving people fives.”

Freer and Nickens both said that the members of Lady Antebellum couldn’t have been more welcoming.

“It’s just a huge privilege,” Freer said. “I can’t say how positive and fun the experience was. … All the guys in the band were like, ‘Let’s just have fun,’ and we did. It was a blast. It was a real treat for the band and for Mason Nation, and I think the whole region. We’re D.C.’s band and we’re really happy to do stuff like that.”

Nickens wasn’t all that familiar with Lady Antebellum before Saturday, but he’s been listening to their music in the days since and said they have a standing invitation to come to Fairfax.

“As I said to them, you think this was fun with 30 members?” he said. “Y’all need to come to a game and I’ll have 200 backing you up.”