The driver reportedly parked the truck, then took off in another car, while the musicians climbed on top of the van and began to perform.
The band members were arrested, but the locked truck remained in the middle of the freeway with no keys in sight.
Police attempted to move the truck using a CHP cruiser, but the move only generated a lot of smoke from the cruiser's spinning wheels.
A heavy-duty tow truck towed the vehicle away, but not before the incident caused a major traffic backup.
Police said the musicians could face charges of obstructing traffic. It is unknown how long the band played.
The group, whose credits include "Traffic Jam 101," says on its website it is dedicated to helping homeless children.
The Associated Press contributed to this story.
