Stasis, it seems, is never an option for Jenks Miller. With the adventurous kind-of-metal outfit Horseback, Miller stretches strains of noise, black metal, doom and blues across albums that play like ominous expeditions. Even in the more restrained country-rock of Mount Moriah, Miller’s guitar offers a sense of adventure, itching to stretch beyond the genre into new territory. Various experiments under his own name have explored harsh electronics, subtle drones and folk-rock mutations.

So it should be little shock that Miller, never one to idle, recently announced two forthcoming releases. The first, a three-CD collection of Horseback rarities called A Plague of Knowing, arrives Aug. 20 via metal powerhouse Relapse Records. It collects limited vinyl releases, live cuts and new material Miller says will help fill the gaps between Horseback full-lengths. The second, Spirit Signal, is an improvisational collection to be released under Miller’s own name by the experimental New York label Northern Spy on Sept. 3.

Recorded earlier this year, Spirit Signal finds the usually meticulous Miller embracing his improvisational impulses, with six pieces that were each developed, recorded and mixed within a single day. The cover, a photo by local artist and WXYC DJ Julianna Thomas, was taken during a period of dense fog in Chapel Hill, at roughly the same time Miller was recording the album.

You can download “Through the Fog” in exchange for an email address: