Taylor Swift is pulling out all the stops on her Eras Tour!

Taking the stage in Las Vegas, Nevada Saturday, Swift treated the sold-out crowd at Allegiant Stadium to a special surprise from Marcus Mumford.

The “Anti-Hero” singer was joined on stage by the Mumford & Sons singer for a special performance of “Cowboy Like Me,” off Swift’s 2020 release, evermore.

Explaining the origin for evermore to her fans, Swift revealed that it was Mumford who lent his home studio to her during the COVID-19 pandemic, to help her record the sister album to folklore.

“I could not find a studio, essentially, and so Aaron was like, ‘OK, let me call around and see if there’s anyone who’s cool and nice and generous and might be willing to offer up their home studio — if you do the right amount of testing, you’re totally locked down, you’re fully quarantined,” Swift shared. “So I was like ‘Please, I really hope somebody comes through. And so he calls me up and he’s like, ‘I have really, really good news. Marcus Mumford said that you could record at his home studio.'”

She continued, “First of all I’m so excited that he’s saving us, because, without this trip, we couldn’t have recorded — five or six of the songs on evermore came from me getting in a car, driving six hours out into the country, past thousands of beautiful sheep, to Marcus Mumford’s beautiful house where he has a studio. So, I got to do this.”

It was there that the pair collaborated on “Cowboy Like Me,” with Swift telling the audience that she was hesitant to ask the Mumford & Sons frontman to lend his talents to the album.

“I didn’t want to be weird about it. So, I was like, I wonder if he’ll wander in. If fate will have him wander into the studio at the right time,” Swift told the crowd. “So, sure enough, we’re recording a song and he wanders in at the perfect time, and just kind of started humming a harmony, and I sort of turned to him as if I hadn’t been thinking of it the whole time.”

“I turned to him, and I was like, ‘Oh, you sound really good on that harmony, wonder if maybe, you might sing on this song?'” Swift continued, “And he was like, ‘Yup, would love to.’ And so, because essentially of Marcus Mumford, we have a lot of the songs that probably, I don’t know if we would’ve been able to put out evermore when we did, as quickly as we did, and we also have a gorgeous harmony on a song called, ‘Cowboy Like Me.'”

It was then that Swift brought Mumford out to the audience’s screams and applause. Swift, who was strumming an acoustic guitar, took the lead during the performance, with Mumford, also on the guitar, supporting the singer by doing backup.

Amongst the sold-out crowd were some celeb fans too, namely fellow country star, Shania Twain, who shared a video of her dancing to Swift’s hits on her Instagram Stories, writing, “WHAT A SHOW!”

Swift kicked the highly anticipated Eras Tour off in Glendale, Arizona, earlier this month, and has been performing upwards of 40 songs each evening, oftentimes without taking a break. Each concert has lasted more than three hours, with songs spanning across Swift’s 17-year career, including mashups of her older tracks like, “I Knew You Were Trouble,” to her newer songs from Midnights, including “Lavender Haze” and more.

For more on the Eras Tour, check out the video below.