Smash Mouth performed for hundreds of people over the weekend in South Dakota.
The rock band played during the 80th annual Sturgis Motorcycle Rally.
It's a massive event that typically draws roughly half a million people to the small town.
The gathering is one of the largest to be held in the US since the start of the pandemic. CNN reports many in the audience were not wearing masks.
Experts say they're concerned it could be a super-spreader event.
Many attendees travel from all over the country -- including coronavirus hotspots -- and could bring infections back home when they return.