The 1960s and 1970s are littered with countless soul and funk bands that are largely forgotten today. Some made genuinely exciting music; others, mediocre tracks with stellar moments, used as source material by hip-hop producers decades later. Only one can lay claim, though, to still being in high school when their greatness was first revealed.

In "Thunder Soul," a new documentary on legendary Texas high school group Kashmere Stage Band, director Mark Landsman gives a history lesson for funk and soul enthusiasts while documenting a touching reunion and tribute for the band’s charismatic leader.

Before Kashmere Stage Band, high school bands primarily looked to jazz standards as the basis for their catalogues. It was safe, anodyne and toothless, but pleasing to the mainly white audience. Under the tutelage of Music Director Conrad "Prof" Johnson, KSB brought new life to an old format, mixing jazz with funk and soul and adding elaborate, choreographed routines to the set. No one had ever seen anything like it; a group of 20-plus teenagers, all seemingly prodigies, playing with an intensity and emotion that their peers couldn't fathom. The band would go on to win numerous national championships, tour Europe, Asia and Australia and release a series of singles.

But as the film, executive produced by Jamie Foxx, shows, music was more than just a pleasant diversion for most of the band. In a poor section in Houston, many grew up with absent fathers and turned to music as a surrogate outlet for other, more illicit activities. Johnson became as much a father figure as band leader, instilling its members with a sense of self-esteem not found on any test grade.

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Thirty years later, with Johnson still alive but in ailing health, the band reunites to perform one last show for their leader. Many hadn't picked up their instruments in years, yet Johnson’s influence and support continued to resonate with them long after they left high school. The film intersperses interviews with Johnson with historical and current footage of the band and its supporters (including DJ Shadow, who sampled KSB for "Holy Calamity (Bear Witness II)" and Stones Throw Records' Eothen "Egon" Alapatt, who released a series of the band's music on his Now-Again Records imprint).

But if "Thunder Soul" was only about the music — which remains some of the best funk ever recorded — the film would likely preach to the converted and become another document for a niche audience. In focusing the film on Johnson and his contributions, both musically and socially, to each member, Landsman augments the musical documentary aspect with a more touching human element that will hopefully attract a bigger audience than music nerds and cratediggers.

Landsman captures Johnson at 92, frail, weakened, but still cognizant and appreciative of his students' dedication and aware of his own influence, both on the class and the genre. It's a stirring tribute to an unsung hero, one whose deeds went far beyond horn blasts and snare fills.