Right now, as you presumably already know, Taylor Swift is in the midst of her Eras Tour, a vast and oddly moving stadium spectacle where virtually every moment is intricately planned-out and choreographed. But there’s one part of the show that allows for some spontaneity: The segment where Taylor plays two acoustic songs that she’s only planning to play once per tour. Last night, that surprise-songs set included a live debut.

Last night’s Eras Tour show was the third and final set of a three-night stand at Gillette Stadium, outside Boston. Saturday night’s set took place amidst a huge downpour, which left’s Swift’s piano waterlogged and useless on the next night. So she played two songs on acoustic guitar. The second was “Red,” the much-loved title track from her 2012 album. The debut was “I Think He Knows,” a deep cut from Swift’s 2019 album Lover. That LP never got its own tour, so she’s just getting to that song now.

As I saw for myself a week and a half ago, Taylor Swift fans are serious. They sing along at full strength with all of her songs, including the deep cuts that come up as surprise additions to the set. Below, watch fan-made videos of “I Think He Knows” and “Red” from last night.

This coming weekend, Taylor Swift is set to play three shows at MetLife Stadium, just outside New York. Those will be the last shows on the tour with Phoebe Bridgers as the opener; the rest of the shows will have Girl In Red, MUNA, or HAIM.