The Quadra is an analog synthesizer made by ARP Instruments between 1978 and 1981. This lush and beautiful sounding keyboard has four unique sound generating systems, bass, strings, poly synthesizer and lead synthesizer. Each is independent and has individual outputs as well as routing through the onboard mixer. In a sense, the beloved Quadra is part ARP Odyssey, String Ensemble and Omni in a package with tons of blending and I/O options.