Thousands of merrymakers thronged around the city’s Christmas tree Friday evening, waiting for the moment when the lights would come on and fireworks would crackle across the downtown Waco sky.

A record crowd estimated at nearly 8,000 gathered for the kickoff of the three-day Waco Wonderland event at Heritage Square. And hiding in plain sight was an unassuming pair of professors, armed with sheet music.

On cue, Baylor classicist David White and mathematician David Ryden broke into the “Hallelujah Chorus” with scores of other local choristers planted in the crowd, as part of a “flash mob” that added to an emerging Waco tradition.

“I’m in the Central Texas Choral Society, and most of us have sung this many times,” White said. “I’m so glad we can be part of this.”

The fun continued through the weekend with a Saturday run and a Christmas parade, along with more attractions at Heritage Square on Saturday and Sunday, including Santa visits, entertainment, a Ferris wheel, a synthetic ice rink and a three-story snow tube course.

The fifth-annual event was expected to draw a record 15,000 people over the weekend, said Jonathan Cook, a city parks and recreation official who helped organize the event.

“This has really become a family tradition in Waco,” Cook said. “We’ve got beautiful weather, and obviously, downtown Waco is just the place to be right now. We have tourists from around the state, and a lot of local people. … It’s become a regional draw.”

The turnout might have been hard to imagine a few years ago, before the city, the Public Improvement District, City Center Waco and local businesses decided downtown needed a big holiday festival.

The low point was in 2012, after smaller holiday events fell by the wayside. City council members gathered around a small tree on a windswept parking lot, flicked the lights and headed inside. One council member at the time said she was “almost mortally embarrassed” by the ceremony.

Wonderland started the next year as an eight-day event and has drawn healthy crowds since, though cold weather last year crimped attendance.

“It’s been a complete transformation,” Cook said. “It’s cool to see how Waco comes together. This event shows how far we’ve come in Waco and how much downtown has grown.”