If you're a psych nerd or garage geek, chances are strong that you're familiar with Brown Acid, a recurring series of compilations from RidingEasy and Permanent Records that dusts off and compiles rare cuts from heavy metal's bluesy, primordial days in the late '60s and early '70s. The vast majority of the bands featured in the collections — appropriately referred to as "trips" — are no longer with us; if you weren't a member of the Boomer set, chances are you missed out. Fortunately, we've got these intermittent, riff-filled time capsules to bear secondary witness to said molten nuggets.

For those heads yet to take the deep dive, you'll soon get your chance: Brown Acid: The Fourth Trip is set to hit shelves on April 20, the trippiest day of the year. Ahead of its release, RidingEasy and Permanent have dusted off a track from Zekes, a vastly underrated hard rock group from California who were among the first West Coasters to spike their psych with the leaden riffs that would, in time, become a cornerstone of heavy metal. Their epic jam, “Comin' Back,” was almost lost to time, but the compilation's producers managed to snag the sole surviving 1/4” master tape from Hollywood’s now-defunct Demars & Duffy Music label. We're really glad they did — it rips. Listen below.

Brown Acid: The Fourth Trip is due out on April 20 via RidingEasy. Pre-orders are available for the digital version over on Bandcamp; physical pre-orders can be obtained via RidingEasy.