Over the years, Nirvana box sets have mined the vaults for demos and unheard music, but it appears as though we may not have heard the last of original material from Kurt Cobain.

In a new press release touting HBO's documentary lineup for 2015, it's revealed that the highly anticipated 'Kurt Cobain: Montage of Heck,' set to premiere May 4, will include "previously unheard originals" from the Cobain catalog.

Cobain's family gave director Brett Morgen full access to Cobain's archives, including his never-before-seen home movies, recordings, artwork, photography, journals, demos, personal archives and songbooks. As expected, the film will feature dozens of Nirvana songs and performances, but the addition of the "previously unheard Cobain originals" is definitely a certain drawing point for any fan of the late rocker.

In addition, the press release confirms the official premiere date for 'Kurt Cobain: Montage of Heck.' Circle May 4 on your calendar for the premiere. Cobain's daughter, Frances Bean Cobain, is serving of executive producer of the film.

You Think You Know Nirvana?

See the Yearbook Photos of Kurt Cobain and More Rock Stars: