Acid house is a variant of house music characterized by the use of simple tone generators with tempo-controlled resonant filters. It began in the mid-1980s, when producers of house music discovered that they could create interesting sounds with the Roland TB-303 analogue bass synthesizer by tweaking the resonance and frequency cut-off dials as they played. Acid house music became a central part of the early rave scene in the U.K., and the yellow smiley became its emblem.
