Stoner rock and stoner metal are interchangeable terms describing sub-genres of rock and metal music. It combines elements of psychedelic rock, blues-rock and doom metal. Stoner rock is typically slow-to-mid tempo and features low-tuned guitars, a bass-heavy sound, melodic vocals, and 'retro' production. The genre emerged during the early 1990s and was pioneered foremost by the California bands Kyuss and Sleep.