For a decade starting in the late ’60s, the Kashmere Stage Band - a funk-infused outfit rooted northeast Houston’s Fifth Ward - built a reputation as the most formidable high school band in the country.

Under the leadership of Conrad O. Johnson Sr., a prodigious musician in his own right - he once played with Count Basie - the band zigged where others zagged, embracing the sounds, and moves, of James Brown and Otis Redding while its peers were mimicking the ossified standards of ’40s big bands.

Mark Landsman’s documentary Thunder Soul recalls the band’s history while following an effort to reunite alumni for a special tribute concert to the ailing Johnson, who’s shown celebrating his 92nd birthday. When they finally gather in the hallowed band room — which looks unchanged from when they graduated, due more to budget restrictions than a will to preserve the past — we realize some of Johnson’s former students haven’t picked up an instrument in over 30 years. They oil up the trombones, blow the cobwebs off the French horns and set about getting their groove back.