It’s been three years since we’ve heard from San Diego’s Earthless, who previously caught our attention by way of their excellent third album From The Ages. Despite the substantial interval since, they remain atop the growing heap of bluesy proto-metallers running around the continental 48, thanks to their essentialized approach. Earthless boil their vintage style down to almost nothing — they’re an instrumental three-piece that rely solely on propulsive rhythms, the occasional keyboard wash, and guitarist Isaiah Mitchell’s pedalboard-freakout soloing to do their damage. That they can effortlessly hold your attention through sprawling extended-jam cuts that feature no vox and few riffs is a testament to their relentless shred powers.

Earthless are working on a fourth LP that should be out later in 2016, but they’ve dipped their toes back into the recording game with “Acid Crusher,” a side-length cut that comprises half of a split LP with hilariously named fellow San Diegoans Harsh Toke. Despite the menacing title, “Acid Crusher” showcases Earthless at their most restrained and minimalistic. It’s basically one big 15-minute vamp, krautrockish in its repetitive restraint. Watery organs and bassist Mike Eginton’s patient thrum carry most of the song, but Mitchell blows the roof off with some truly Hendrix-esque wah abuse before it can wind down. Harsh Toke mine roughly the same vein of resiny ore as Earthless, but deliver a denser final product — their 20-minute jam “Mount Swan” leans heavily on tumbling-down-the-mountain riffs and features a warbling vocal that occasionally fights through the layers of instrumental haze. Of course, this is self-described “acid rock,” so Harsh Toke’s structures periodically disappear into a paisley-patterned vortex of noise throughout the tune. Listen to both cuts below.

Acid Crusher / Mount Swan will be out 5/27 via Tee Pee Records.