Sequential Circuits (also known as Sequential or SCI) was a synth manufacturer formed in 1977. The founders were Dave Smith and John Bowen on the technical side, and Barb Fairhurst taking care of the business side of the operation. They released a sequencer, the Model 700, that year. In the meantime, they were working on the ground-breaking Prophet-5, which they released in 1978. The Prophet-5 dominated the market for polyphonic synthesizers until 1983. In the meantime, the company released a variety of variations on the Prophet-5 theme, both polyphonic and monophonic. The high point of this period was probably the Prophet-T8, an eight-voice synth with a piano-weighted keyboard with polyphonic aftertouch.
In the mid-'80s, the company delved into samplers, with the Prophet 2000 and 3000. These were well-liked by the performers who bought them, but they were priced higher than the comparable models from E-mu Systems, and sales were slow. The company's last product was the Prophet VS, the first synth to use the vector synthesis concept. The Prophet VS was released just months before the company collapsed in 1987. In December of that year, Yamaha acquired the company and shut down its production. They sold the remaining stock, along with technical documentation and software, to Wine Country Productions. Wine Country has been offering parts and service for vintage Sequential Circuits synths for many years, but their parts stock is now nearly depleted.
A team of engineers led by Smith went to work for Yamaha after the acquisition of Sequential They designed the SY22 and TG33 vector synths for Yamaha. Later, Yamaha assigned them to do projects for Korg, which Yamaha owned at the time. The group developed the Korg Wavestation, which was basically a re-creation of the Prophet VS with some improvements.
Sequential was instrumental in the development of MIDI. The company had developed a proprietary remote control bus for the Prophet-5, as had Roland for its products of that era. A chance meeting between Smith and Roland's Ikutaro Kakehashi led to the formation of a trade group that developed the original MIDI standard. In 1982, Sequential's Prophet-600 became one of the two first synth models to be factory-equipped with MIDI, along with Roland's JX3P. Smith and Kakehashi received Grammy awards in 2013 for their work on MIDI.
Smith launched a new synthesizer manufacturing company, Dave Smith Instruments, in 2002. In 2015, DSI acquired the rights to the Sequential Circuits name and trademarks. They launched the Prophet-6, a re-creation and update of the Prophet-5, under the Sequential name.