Here’s a spirit-lifting documentary about black transgender electronic music pioneer Glenn Copeland. It begins with the story of how he was “discovered” a few years ago, aged 72. At home in Canada, Copeland reads the email he got in 2015 from a record shop owner in Japan: the guy offered to buy any spare copies of Keyboard Fantasies, an album Copeland self-released in 1986 on cassette. At the time he was known as Beverly Glenn-Copeland, and the album is a trippy mix of electronica, folk and new age, overlaid with Copeland’s sumptuous contralto tenor; it’s now seen as his masterpiece. He had pressed 200 tapes and sold around 50.

I could watch Copeland talking for hours. With his smiling eyes he radiates life and happiness, basking in autumnal success – the world has finally caught up with him. He was born Beverly Glenn-Copeland into a middle-class family in Philadelphia. At 17 in the early 60s, he was one of the first black students at a prestigious Canadian university, studying classical music. Homosexuality was still illegal in Canada, but Copeland was open about his relationship with another woman. His parents carted him off to a psychiatric hospital for electroshock “therapy” but he escaped. After dropping out of college, Copeland recorded a couple of albums, both commercial disasters. Then in the early 80s he discovered computers – “and I was off to the races”.

Copeland recorded Keyboard Fantasies using an Atari computer, a synth and a drum machine. It was decades ahead of its time, and the film mostly follows Copeland on tour playing to young audiences who have just discovered him. His band is an adorable ragtag of musicians in their 20s (they look younger, like the kind of A-level students who hang around the art room at lunch). Often music documentaries feel padded out with filler but honestly I could have spent another hour in Copeland’s company.

• Keyboard Fantasies is released on 12 November in cinemas.