Acid house is a spawn of house music which generally utilizes the structure of its predecessor, and emphasizes a repetitive, hypnotic and trance-like style, often with samples or spoken lines rather than sung lyrics. Acid house instrumentation typically consists of analog synthesizers (predominantly the Roland TB-303), 4/4 beats, pop vocals enhanced with a large amount of echo and reverb, symphonic choirs, claves loops, and in many cases, effects similar to radio tuning. Acid house is often played at clubs and raves, and has also spawned acid house parties. The Chicago-based group Phuture are typically considered the pioneers of the genre.