Bear McCreary is pulling a reverse Trent Reznor.

While the Nine Inch Nails front man transitioned from the rock world into film composing, McCreary, whose scoring credits include Battlestar Galactica, The Walking Dead and the God of War video games, is now releasing The Singularity, an orchestral metal concept album.

A long in-the-works passion project featuring music McCreary wrote when he was 15, The Singularity is filled with sci-fi images and themes that are further explored in an accompanying graphic novel. However, the core of the album, McCreary says, is very personal.

“That’s the reason I made The Singularity in the first place, is I had a story I wanted to tell,” McCreary tells ABC Audio. “I had emotions that were exploding out of me. I wanted to create something that was very emotional. That’s the first word I use when I describe the music to people.”

To help tell that story, McCreary recruited big-name rockers including Slash, System of a Down‘s Serj Tankian and Slipknot‘s Corey Taylor. Tankian sings the song “Incinerator,” which McCreary originally wrote as a “love letter” to System of a Down.

“For him to come back to that kind of, like, System style, and he heard what I was going for and sing that way on my record, it was an honor,” McCreary says. “I was thrilled.”

Slash, meanwhile, guests on two tracks, including the 11-minute “The End of Tomorrow,” which was inspired by McCreary’s love of Guns N’ Roses‘ “November Rain.”

“When I heard Slash play it, man, you hear that tone, to me, it just takes you somewhere,” McCreary says. “He’s just one of the most legendary guitarists to have ever lived.”

The Singularity is out now. McCreary will play a Los Angeles concert, featuring guests including Slash, on May 12.