Acid house Emphasizes a repetitive, hypnotic and trance-like style, often with samples or spoken lines instead of lyrics. It has core electronic "squelch" sounds that were developed around the mid-1980s, particularly by DJs from Chicago who experimented with the Roland TB-303 electronic synthesizer-sequencer. Ambient house Combines elements of acid house and ambient music, typically featuring synth pads and "atmospheric style" vocal samples. It emerged in the late 1980s. Afro house African music mixed with a house beat.