Cold Spring’s vinyl split Sargo / Posidonia pairs Sleep Research Facility and Llyn Y Cwn — two Dark Ambient practitioners who work in subterranean drones and oceanic hiss. Sleep Research Facility’s side favors cavernous low-end and long decay, while Llyn Y Cwn leans on brittle field recordings and metallic reverbs unspooling at a glacial pace. It’s a focused vinyl statement that rewards late-night spins.