It's of Chilton, Jim Dickinson, Sid Selvidge and Marcia Hare recording "Like Flies on Sherbert."
Either Randall Lyon or Gurdonian (!) Tav Falco shot the footage, according to local musician/videographer/man-about-town Greg Spradlin, who just posted it on his Vimeo page
It won't be up for long, Spradlin says. So soak it up while the soakin's good.
And don't worry if get prolonged beeping. It takes it about 20 seconds to kick in.