An album of unreleased music by grunge icon Kurt Cobain will come out in November to accompany a documentary on the late Nirvana frontman, the director says.

In researching "Montage of Heck," filmmaker Brett Morgen discovered more than 100 early cassettes recorded by Cobain, who grew up in the lumber town of Aberdeen, Washington.

Some fans have described the music as the equivalent of a solo album from the music legend, who killed himself in 1994 at age 27.

Giving a release date for the first time, Morgen told the AwardsLine website that the music would come out as a soundtrack to "Montage of Heck" on November 6, the same day the documentary goes on sale as a DVD.

The unheard music includes a 12-minute acoustic song by Cobain, who was known with Nirvana not only for his searing electric guitar but also his unplugged work.

Morgen recently told music industry journal Billboard that the soundtrack would also include a comedy skit in which Cobain plays various characters.

Morgen told AFP earlier this year that the newly discovered cassettes showed the various sides of Cobain: "The romanticism, the honesty, all of these different emotions."

"When I first heard it, I was in the storage facility and I had no prior knowledge of it. I put it on and I immediately felt like there was some sort of portal into his mind, like it was one of the most pure expressions of Kurt that I encountered -- maybe more than in most of his songs," he said.

Morgen made "Montage of Heck" with the cooperation of both Cobain's widow and fellow rocker Courtney Love and their daughter Frances Bean Cobain, who has had a complicated relationship with her mother.

Released in theaters and on HBO, "Montage of Heck" was nominated for a number of Emmy Awards, including Outstanding Documentary or Nonfiction Special.