The Grand Ole Opry turns 90 this year, and over the weekend, country stars came to Nashville to celebrate the occasion -- and to flawlessly sing "Happy Birthday" to the country music institution onstage at the Grand Ole Opry House.

During the Opry's 90th Birthday Bash, which took place on both Friday (Oct. 2) and Saturday (Oct. 3), a larger-than-life birthday cake was rolled onstage during the festivities, as each evening's performers lined up and launched into the celebratory song. Their harmonies were impeccable -- but would you expect anything less?

When the song was finished, brightly colored balloons fell from the ceiling, adding to the party atmosphere. Press play on the video above to see Friday night's performance, which featured, among others, Little Big TownLarry Gatlin and Lorrie Morgan.

The celebration of the Opry's 90th birthday has been one for the record books. In addition to the weekend's scheduled performances, there were some surprise collaborations, and Good Morning America co-host Robin Roberts even made an appearance.

"I felt very unworthy, and still do, to a certain extent, just because it is ... the Grand Ole Opry," Carrie Underwood said backstage on Saturday night. "[The Opry] loves what country music is now, but it loves the past as well. And it loves artists that just continue to do what they love."

Notes Trace Adkins, "My membership in the Grand Ole Opry is the thing I’m most proud of in my whole career. I take it very seriously. I know when I’m out there, I’m a representative of the Grand Ole Opry. I’m very cognizant of that all the time.”

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