Willie Nelson gives back to a show that has helped him throughout his career in a new documentary called A Song For You: The Austin City Limits Story. The singer sings Austin City Limit's praises in the film, which will premiere at the 2016 South by Southwest Festival in Nelson's own Austin, Texas, next month.

Described as "the ultimate backstage pass to 40 years of incredible music," the two-and-a-half minute trailer highlights four decades of music from the longest-running music show in television history. The film features interviews with producers and artists, as well as showcases some of the legendary performances throughout the past 40 years. Appearances in the film are made by Nelson, Beck, Bonnie Raitt, Jeff Tweedy, the Pixies, Loretta Lynn, Ray Charles, Dolly Parton, Brittany Howard of Alabama Shakes, Townes Van Zandt, Buddy Guy, Leonard Cohen, Kris Kristofferson, Marcia Ball and many more.

"I've been associated with Austin City Limits since the beginning," Nelson says in the A Song for You trailer. "I did the first show."

Meanwhile, other artists discuss their nerves to play the historic television show as the tradition it holds is undeniable. The trailer highlights several performances by country legends Nelson, Kristofferson and Merle Haggard, as well as Miranda Lambert, Jack White, Coldplay and Dave Grohl.

"I don't care about being inducted in the Rock & Roll Hall of Fame," Grohl says in a clip. "I got to play Austin City Limits."

Directed by Keith Maitland, the film also discusses the difficulties the show had as one producer admits that each year they never knew if they would be funded. Thankfully, somehow, they always found a way.

"I'm really glad to see it still doing well and getting better all the time," Nelson concludes.

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