Iron Butterfly’s 1968 debut album “Heavy,” is a gritty, organ-driven slab of psychedelic rock that laid early groundwork for heavy metal. With thick guitar riffs, swirling keys, and Doug Ingle’s haunting vocals, the album delivers a raw, moody atmosphere throughout. Tracks like “Possession” and “Unconscious Power” showcase a band experimenting boldly with weight and distortion, creating a sound darker than most of their psychedelic peers. Though not as iconic as In-A-Gadda-Da-Vida, Heavy stands on its own as a powerful, if somewhat uneven, early hard rock statement. Its brooding energy and proto-metal edge still resonate today with fans of late '60s rock evolution.