Jamie Foxx isn’t in “Thunder Soul,” but he plans to be its most vocal ambassador.

The stirring documentary tracks the reunion of 30 members of the stage band of the predominantly African-American Kashmere High School in Houston as they reconnect for a tribute concert for their former teacher, 92-year-old Conrad O. Johnson.

Many of them haven’t picked up an instrument in decades and it’s touching watching them struggle to remember the old chords and coordinated dance moves, all to honor the man they affectionately called “Prof.”

Though Foxx hails from Texas, he was just a kid when Prof and the Kashmere Stage Band were making national headlines from the late-'60s to mid-'70s for being anything but a typical school band. Their powerhouse funk performances – many of their songs were original Prof compositions -- led to live appearances in Europe and Japan and, in 1972, Kashmere won the All-American High School Stage Band Festival in Mobile, Ala., while segregationist George Wallace was state governor.

The meaty story led Foxx, a musician himself since childhood, to get involved in “Thunder” post-production.

“As soon as I saw [the movie], I said, is there any way I can get the word out? I watched it in my office and I was brought to tears. It moves you, man,” Foxx said recently from his home in Los Angeles. “You gotta believe in magic and miracles.”

“Thunder Soul” opens in four cities, including Atlanta on Sept. 23, and will continue to expand wide through Oct. 14.

In a move similar to when Oprah Winfrey endorsed “Precious,” the film is now being marketed as “Jamie Foxx Presents,” a tactic he supports because, “I don’t want this movie to go unseen and unheard.”

Aside from the touching human elements in “Thunder Soul” – a real-life twist at the end is both heartbreaking and inspirational – there is the more subtle point of the importance of music education in schools.

Foxx is hopeful that the documentary will find its way into classrooms, even as instruments continue to disappear, their importance diminished with every rainfall of budget cuts.

“My grandmother had me start playing piano when I was 5 and I felt bad because everyone was out there playing football. But then I got a classical piano scholarship [to United States International University in San Diego],” Foxx said. “Music can do something different, it can take you somewhere. Extracurricular activities make things better. The clichés work.”

Foxx’s involvement in music also stretches to his Fox City Records label – he’s producing a handful of new acts – and his determination to resurrect “Showtime at the Apollo,” which ended in 2008.

“That’s another classic thing we were losing. How do we lose that? Aretha, Michael Jackson, everybody has done that stage. I wanted to bring new life to it,” Foxx said, adding that the show will air on BET this fall.

Foxx’s commitment to “Thunder Soul” is further proof that once the importance of music is instilled, it never dissipates.

Movie preview

“Thunder Soul”

Starring Conrad Johnson. Directed by Mark Landsman.

Rated PG for brief strong language. At metro theaters. 1 hour, 23 minutes.