In the 1977 sci-fi classic Close Encounters of the Third Kind, five electronic-sounding notes allow humanity to communicate with aliens. The source of those notes likely came from the ARP 2500—a modular, analog synthesizer. Designed by former NASA electrical engineer Alan R. Pearlman, the instrument’s most significant innovation is its matrix of patchable sliders. These sliders stand in stark contrast to the loose patch cables found on the more conventional Moog and Buchla systems of the time. The company’s first instrument was not a commercial success however—only selling about 100 units.