Thousands of people packed the waterfront last weekend to watch Thunder Over Louisville, the largest annual fireworks display in North America.

But it wasn’t long after the sky went dark and the music stopped that — wait for it — people took to Twitter to complain about this year’s event.

The most common criticism? The music.

Louisville Orchestra conductor Teddy Abrams selected the soundtrack, which was filled with songs that have local ties. They were then edited and mixed by Thunder producer Wayne Hettinger.

It was an innovative choice, but one that also divided people into two camps: those who showered Abrams with praise for his selections, and those who complained the music was disjointed from the fireworks. One commenter likened it to watching a video with a sound delay.

Complaints are par for the course. But why was this such a common one?

“Music tends to make people more sensitive to temporal irregularity,” says Elizabeth Margulis, who directs the Music Cognition Lab at the University of Arkansas.

She says music is more effective than visual stimuli in alerting people about patterns or the rhythm of upcoming events.

“So in the fireworks case, just the fact that there’s music is probably orienting people more to this time dimension and kind of exposing the mismatch,” Margulis says. “Just the fact that there’s music there is doing that.”

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Miriam Lense of Vanderbilt University’s Program for Music, Mind and Society says our brains have a particular specialty: They can integrate information across the senses really well.

“So if that information wasn’t aligning [and] the people or the attendees were expecting that information to be aligned, that could have been one reason for the unsettling experience,” Lense says.

In fact, she says, there is far more space in our brains dedicated to the integration of our senses than to isolating them.

This is everywhere in our daily lives.

Mentally walk through the process of making coffee. You probably envision both the sound of the coffee percolating and the little light that flickers on to let you know it’s brewing. It’s a complete sensory package (not to mention the aroma).

If you need more evidence, Margulis points to a study where researchers had participants describe the pitch difference between two notes, which is called an interval.

“They found that people are pretty much as good at judging the size of these intervals if they are just looking at the images of the face producing them, and not even hearing anything at all,” she says. “So that’s how tightly intertwined what we see is with what we hear.”

Margulis says there’s something really special about the fact that we have all this different sensory information bombarding us all day long — yet we have this unified experience of the world. It’s like our brain is performing magic tricks all day long.

So, that’s why it’s so disconcerting when what we see and hear don’t connect.

And that’s why, science aside, Miriam Lense totally gets what some members of the Thunder audience were feeling.

“I certainly have been to fireworks displays where it’s not coordinated with the music,” Lense says, laughing. “So I know that experience of when you expect the largest fireworks to come at these large times on the music when the beat is expecting something to be happening. I think I get where your audience is coming from.”