Acid techno is the term used to describe a style of techno that developed out of late 1980s Chicago Acid house. Acid house was essentially house music made with a specific sound, obtained by using very distinctive instruments created mainly by Roland, such as the TB-303 for bass and lead sounds, and the TR-909 and TR-808 for percussion. Acid specifically refers to the use of the Roland TB-303, or any other synthesizer designed to emulate its unique sound. While modern electronic instruments have memory banks of different sounds or patches, these machines had to be manually set by adjusting control knobs. The acid sound was obtained by either setting these controls to extreme parameters, or manipulating these controls in real-time as the track was being recorded, something record producers would call tweaking. Acid techno is created in the same exact way Acid house is, the difference being that House music has a specific format that includes melody and the potential for vocals and traditional western popular music structuring, where as Techno music requires no melody or harmony and focuses more on rhythm and texture, which is why it is most commonly viewed as having less commercial potential.