There’s a joyous, tribal quality to Animal Collective’s sound. It’s as if some isolated, indigenous peoples turned their tool-making skills to sequencers, with a warped copy of “Pet Sounds” as its melodic guide.

Monday night at St. Petersburg’s packed State Theatre, the group proved it could be as enchanting live as on disc.

AC’s sound could be classified as experimental, but it’s an experiment that feels natural, never forced. Its music may be machine-made but it’s driven by humanity.

A giant plastic ball hung in front of the stage serving as a video screen while a kinetic light show matched the rhythmic pulse for intensity and unpredictability.

Still, the most striking part of the light show may have been Brian Weitz’s headlamp, bobbing, wagging and shaking in time to the music.

The songs didn’t so much segue as morph into one another, changing shape so naturally the change was barely noticeable until a familiar bit from, say, “Also Frightened” caught the ear.

It may not be possible to create music that’s entirely new, but Animal Collective at least arranges the parts into new and exciting shapes. It’s pop music with everything except the structure, where once familiar harmonies and melodies have the shock of the new.

Openers Black Dice also fit the experimental bill, if “experimental” is a polite way of saying “unlistenable.”

Actually, the trio’s unrelenting barrage of sight and sound could have made for an intriguing 30-minute set. Unfortunately, it went on for an hour, the last half of which was spent mostly repeating itself to ever dwindling returns. 

The problem wasn’t the battering-ram like intensity of the sound so much as that it was entirely static. The music plopped itself down and refused to budge. There were rhythmic shifts, to be sure, but not so much that dynamics were in danger of breaking out.