Greetings again from the darkness. It's difficult to believe now, but Austin City Limits was once "the little engine that could" … and now it's the longest running music program on television. Willie Nelson played the 1974 pilot, and the rest – as they say – is history … and continues to be history in the making."This is a show about music." That simple quote from the film says a great deal. There is no place to hide on the small stage in the small studio with the audience right on top of you. These aren't music videos, but rather these are the artists performing their songs live in an intimate setting (with the ever-present TV cameras).Director Keith Maitland, who also presented his powerful documentary "Tower" at the Dallas International Film Festival, spends a great deal of time allowing producer Terry Lickona to reminisce and tell stories about how the show has always walked a fine line between success and the threat of cancellation … what's also known as life in public television.Much of the structure of the film is around the show's 40th anniversary and the formulating of the initial class of the ACL Hall of Fame. As interesting as it is to listen to Mr. Lickona and ACL founder Bill Arhos, it's the music that shines here. There are too many clips to name here, and certainly some of the choices speak to the age of the director, but the highlights include a soulful Townes Van Zandt in 1976, a spirited Lightnin' Hopkins in 1979, Ray Charles (and a shot of my head in the crowd) in 1980, the infamous Stevie Ray Vaughn show in 1983, and the always smooth and debonair Leonard Cohen from 1989. There are also clips of The Pixies, Radiohead, Dolly Parton, Buddy Guy and, well, just too many to name … yet somehow not enough.We also see Lyle Lovett's show which was the final filming in the original Studio 6A, before ACL got a building/studio designed just for them (one a bit more fire code friendly). It's a wonderful trip down Memory Lane for someone like me who spent many a night in the old studio, and for those of us who have so appreciated the straightforward approach to music that the TV show has maintained through the years.