Rotten Apple

In this 1980 movie - often included in lists of worst movies of all time - the music of the Future (1994) will sound and look like The Glitter Band crossed with Amy "Knock On Wood" Stewart.

It was also released under the title Star Rock, which couldn't be more glam.

A mish-mash of Phantom of the Paradise, Rocky Horror, Stardust, Thank God It's Friday... with some unique rankness all its own.

The story:

In an uncut two-song prologue of the film named "Paradise Day," Mr. Topps [God] creates heaven and carves the first human Alphie out of a rock, sending Alphie to Earth to meet Bibi. The two take part in the 1994 Worldvision Song Festival. Despite being the most talented performers, they are beaten by BIM (Boogalow International Music) and its leader, Mr. Boogalow, who use underhanded tactics to secure a victory. The duo are approached by Mr. Boogalow to sign to his music label, but they soon discover the darker side of the music industry. Bibi is caught up in the wild lifestyle BIM offers, while Alphie risks his life to free her from the company's evil clutches. He eventually convinces her to run away with him and the pair live as hippies for a year (and produce a child) before being tracked down by Mr. Boogalow who insists Bibi owes him ten million dollars. Alphie and Bibi are saved by the Rapture, and all good souls are taken away by Mr. Topps who arrives on scene in a flying apparition of a Rolls Royce." [Wiki]

The story behind the story:

"In 1975, Coby Recht, a successful Israeli rock producer, was signed to a major label for the first time, that being Barclay Records, which was founded and led by French producer Eddie Barclay. As Recht described working with Barclay, "he really believed in me. But there was something there that I couldn't trust. I don't know why, but the guy looked to me like a villain." His experience with Barclay, as well as being a "moral guy" who never liked what went on in show business, inspired the story of a musical Recht and his wife Iris Yotvat were conceiving for six weeks while in Paris,and the antagonist Mr. Boogalow was based on Barclay. Recht explained that it was "supposed to be 1984, but with music." [Wiki]

So it was essentially a project conceived circa the glam-twilight, that took a while to get made, so got updated with some disco touches.

And in a certain sense it was an anti-glam film:

"Described by Francis Rizzo of DVD Talk as the Faust legend told through the lens of the music industry, The Apple is about a conflict between good and evil, a battle between the pacifistic hippies and show business people who only care about wealth and power. Journalist Richard Harland Smith, categorizing The Apple as an antisemitic "Christian scare film," compared the story to Adolf Hitler's Mein Kampf  and its ending to the Nazi's Final Solution; Smith wrote that the film involves a homophobic protagonist, Alphie, trying to save his "normal" relationship with Bibi from what the film considers satanic, which includes electronic music, glitter, homosexuals, and drag queens." [Wiki]