There are countless bands out there that music writers like to label as “undefinable” or “genre-bending,” or even “experimental” because there just isn’t a handy genre box in which to immediately file them away. It is in this space, especially in the ever-expanding, reinventing, and redefining world of metal, that some of the greatest artistic innovation in history has occurred, sowing the seeds for future bands to draw inspiration.

San Francisco’s three-piece act Grayceon has consistently been one such band since their inception in 2005. Jackie Perez Gratz (who is also a member of San Francisco post-metal group Giant Squid, and has a collaboration resume that includes Neurosis, Om, and Agalloch) lays out delicate vocals and dark cello leads over guitarist Max Doyle's proggy, dirgy riffs and drummer Zack Farwell’s resolute percussion. The best one could do would be to describe their music as sludge—in the vein of early Mastodon or Baroness—with strings in that remind of non-metal bands Murder By Death or Cursive. But the truth is, you really just have to hear it for yourself—especially now that Grayceon have finally returned with their fourth album, IV.

“Unlike our previous albums, IV took us almost five years to make and in many ways is our love child," Jackie Perez Gratz told Noisey. "The songs incubated inside us and grew into what they are today. It really thrills us that it’s finally in the hands of our fans.”

IV is perhaps their most beautiful, complex, masterfully innovative record yet—a mighty feat for a band whose music already exists so completely outside of the mold. It’s out on Friday via Translation Loss Records, and you can stream the whole thing right here ahead of its release.