High Quality Content by WIKIPEDIA articles! Sequential Circuits Inc. (SCI) was a California-based synthesizer company that was founded in the early 1970s by Dave Smith, and sold to Yamaha Corporation in 1987. Throughout its lifespan, Sequential pioneered technologies and design principles that have served as a foundation for the development of modern music technology. Sequential was also pivotal in the planning, design, and support of 1982`s groundbreaking innovation in electronic music, MIDI.