If this was your first time at the Tecate Pa’l Norte festival and you weren’t familiar with the surprise stage concept, you probably freaked out when a tornado-like siren began ringing exactly at 7 p.m. It was no tornado. Instead, the sound alerted attendees that the first surprise artist of the night was about to start performing at the Sorpresa stage.

These artists are not previously announced on the lineup, and a total of two surprise acts perform per day. They are short sets — artists typically have around 10-15 minutes to sing. The first surprise artist on Friday (March 29) was the elusive reggaeton duo Angel y Khriz.

The pair started their set shortly after Belanova had wrapped on the main stage. The reggaetoneros started off with their massive 2005 hit “Ven Bailalo.” They quickly followed it with the equally infectious “Na De Na.” And then time was up. They thanked fans and left the stage.

The second act to take the stage, at 8:52 p.m., was latest regional Mexican breakthrough artist Xavi — setting the perfect vibe for upcoming headliner Peso Pluma. The 19-year-old Mexican-American artist, who kicked off his Poco a Poco Tour in Mexico City on March 28, performed a total of five songs, including “La Víctima” and “Corazón de Piedra.”

The Pa’l Norte festival is taking place March 29-31 at the Parque Fundidora in Monterrey, Nuevo León, in Mexico. Headliners for this year’s edition include Peso Pluma, Blink-182, Maná, Fuerza Regida, Louis Tomlinson and Thirty Seconds to Mars. Kendrick Lamar was set to headline on Friday but canceled his performance because of “unseen circumstances due to logistical issues,” according to a statement by the festival organizers.

Below, see an updating list of all the surprise artists who performed at the Sorpresa stage.

On Beyoncé’s Cowboy Carter, released Friday (March 29), the superstar salutes pioneering country artist Linda Martell, the first Black woman to ever play the Grand Ole Opry in 1969, and, in doing so, is introducing the pioneer to a whole new audience. 

Though she has long retired, the 82-year-old Martell returns on Beyoncé’s album on two segments, both of which address Beyoncé’s refusal to be bound by genre lines. In the introduction to “Spaghettii,” she says, “Genres are a funny little concept, aren’t they? Yes they are. In theory, they have a simple definition that’s easy to understand, but in practice, well, some may feel confined.”

Martell returns on the 28-second interlude titled “The Linda Martell Show,” opening with “Thank you very much,” to the sound of applause. She continues, “This particular tune stretches across a range of genres and that’s what makes it’s a unique listening experience. Yes, indeed. It’s called ‘Ya Ya,’” she says before the genre-bending “Ya Ya” opens to a sample of Nancy Sinatra’s 1966 classic, “These Boots Are Made For Walkin.’”

For many listeners, this is likely the first time they have heard of Martell, who played such a groundbreaking role in country music. Her breakthrough single, “Color Him Father,” peaked at No. 22 in September 1969. The song was the highest-charting song on the tally by a Black woman for more than 50 years until Beyoncé’s “Texas Hold ‘Em” reached No. 1 earlier this year.

On Friday, Martell praised Beyoncé via an Instagram post. “I am proud that @beyonce is exploring her country music roots. What she is doing is beautiful, and I’m honored to be a part of it. It’s Beyoncé, after all!”

Here are seven things you should know about Martell.