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Sequential (company)
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Sequential is an American synthesizer company founded in 1974 as Sequential Circuits by Dave Smith. In 1978, Sequential released the Prophet-5, the first programmable polyphonic synthesizer, which was widely used in the music industry. In the 1980s, Sequential was important in the development of MIDI, a technical standard for synchronizing electronic instruments.

Key Information

In 1987, Sequential went out of business and was purchased by Yamaha. Smith continued to develop instruments through a new company, Dave Smith Instruments. In 2015, Yamaha returned the Sequential Circuits trademark to Dave Smith Instruments, which rebranded as Sequential in 2018. In 2021, Sequential was acquired by the British audio technology company Focusrite. Smith died in 2022.

History

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Sequential founder Dave Smith in 2015

1974–1980: Founding, first products and Prophet-5

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The engineer Dave Smith founded Sequential Circuits in San Francisco in 1974.[1] The first Sequential Circuits product was an analog sequencer for use with Moog and ARP synthesizers, followed by a digital sequencer and the Model 700 Programmer, which allowed users to program Minimoog and ARP 2600 synthesizers.[2] The Model 800, launched in 1975, was controlled and programmed with a microprocessor.[3]

The Prophet-5 (1978), the first Sequential synthesizer. The specific model pictured above is the "Rev 3", first released in 1980.

At the time, Smith had a full-time job working with microprocessors, then a new technology. He conceived the idea of combining them with synthesizer chips to create a programmable synthesizer, but did not pursue the idea, assuming Moog or ARP would design the instrument first.[2] When no instrument emerged, in early 1977, Smith quit his job to work full-time on a design for the Prophet-5, the first fully programmable polyphonic synthesizer. He demonstrated it at the NAMM International Music & Sound Expo in January 1978 and shipped the first models later that year.[2]

Whereas previous synthesizers required users to adjust cables and knobs to change sounds, with no guarantee of exactly recreating a sound,[4] the Prophet-5 used microprocessors to store sounds in patch memory.[5] This facilitated a move from synthesizers creating unpredictable sounds to producing "a standard package of familiar sounds".[4]: 385  The Prophet-5 became a market leader and industry standard,[6] used by musicians such as Michael Jackson, Madonna, and Dr Dre, and by film composers such as John Carpenter.[6] It was followed by the larger Prophet-10, which featured two keybeds and was less successful as it was notorious for unreliability.[7] The smaller Pro-One, essentially a monophonic Prophet-5,[8] saw more success.[6]

1981–1982: MIDI

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Main article: MIDI
Prophet 600 (1982), the first Sequential Circuits synthesizer with MIDI functionality

In 1981, Ikutaro Kakehashi, the founder of the Japanese synthesizer company Roland, contacted Smith about creating a standardized means of synchronizing electronic instruments manufactured by different companies.[9] Smith and the Sequential engineer Chet Wood designed an interface using Roland's Digital Control Bus (DCB) as a basis.[10] This standard was discussed and modified by representatives of Roland, Yamaha, Korg, and Kawai.[11][12]: 20  The protocol was named Musical Instrument Digital Interface (MIDI)[13]: 4  and unveiled by Kakehashi and Smith, who received Technical Grammy Awards in 2013 for their work.[14][15][16] In 1982, Sequential released the Prophet 600, one of the first MIDI-equipped synthesizers.[17] In 1984, they released the Drumtraks, one of the first drum machines with MIDI control.[18]

Various Sequential products [top to bottom]
  • PRO-ONE (1981)[19]
  • Model 700 Programmer (1976)[19]
  • Prophet-5 (1978)[19]
  • Prophet T8 (1983)[19]

1987: Closure

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In 1987 Sequential Circuits released their final product, the Prophet 3000 digital sampler.[20] Only several dozen units were produced before the company went out of business. Smith blamed the closure on the decision to move to computer audio in prior years: "We were too small and under-capitalized, and we were a few years too early in the market ... It drained our resources, so by the time we pulled back to professional instruments, it was too late."[2]

Sequential Circuits was purchased by the Japanese corporation Yamaha. They released no products under the Sequential name and shut it down in 1989,[2][9] following the failure of the TX16W digital sampler.[20] Smith and much of the development team moved to Korg, where they worked mainly on the Wavestation synthesizer.[2][20]

2002–2014: Dave Smith Instruments

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In 2002, after several years of working on software synthesis, Smith opened a new company, Dave Smith Instruments, to build new hardware. Its first product was the Evolver synthesizer in 2002.[2] In 2008, Dave Smith Instruments launched the Prophet '08, conceived as an affordable eight-voice analog synthesizer.[2]

2015–present: Return to Sequential and Focusrite acquisition

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In January 2015, Yamaha returned the Sequential Circuits brands to Smith in a goodwill gesture. This was at the encouragement of Kakehashi, who had worked with Smith to create MIDI. Kakehashi said: "I feel that it's important to get rid of unnecessary conflict among electronic musical instrument companies. That is exactly the spirit of MIDI. For this reason, I personally recommended that the President of Yamaha, Mr. Nakata, return the rights to the Sequential name to Dave Smith."[21]

In 2015, Sequential released the Prophet-6,[22] followed in 2018 by the Prophet-X, which featured sample playback and digitally controlled oscillators.[23] On August 31, 2018, the 40th anniversary of the Prophet-5, Dave Smith Instruments rebranded as Sequential.[24] In September 2020, Sequential announced an updated reissue of the original Prophet-5.[25] Sequential reported revenues of $18.3 million in 2020.[26] In April 2021, Sequential was acquired by the British audio technology company Focusrite.[27] Smith died on May 31, 2022.[28]

References

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Further reading

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[edit]
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Sequential (company)

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Sequential is an American synthesizer company founded in 1974 by engineer and instrument designer Dave Smith, best known for developing the Prophet-5, the world's first fully programmable polyphonic synthesizer, and co-creating the Musical Instrument Digital Interface (MIDI) standard that revolutionized electronic music production. Originally established as Sequential Circuits in the , the company quickly gained prominence in the late with the release of the in 1978, which used technology to allow musicians to store and recall sounds, addressing a major limitation of earlier analog synthesizers. This innovation, combined with subsequent models like the Prophet-10 (1980) and the monophonic Pro-One (1981), established Sequential as a leader in the burgeoning field of electronic instruments, influencing artists across genres from prog rock to hip-hop. In 1983, Dave Smith and Sequential co-developed the MIDI protocol alongside representatives from other major manufacturers, enabling seamless communication between synthesizers, computers, and sequencers—a foundational technology still in use today. The company expanded its lineup in the 1980s with hybrid digital-analog instruments such as the Prophet VS (1982) and Studio 440 (1984), but faced financial challenges amid industry shifts toward digital keyboards, leading to its acquisition by Yamaha in 1987. After a period of dormancy under Japanese ownership—during which the Sequential brand was integrated into Yamaha and later Korg products—Smith reacquired the rights to the name in 2015 and rebranded his firm Dave Smith Instruments (DSI) as Sequential in 2018, reviving the legacy with modern recreations like the Prophet-6 (2015) and OB-6 (2016), developed in collaboration with Tom Oberheim. Under this resurgence, Sequential released acclaimed instruments including the Take 5 (2020), Trigon-6 (2022)—the last project Smith contributed to before his death in 2022—and the Prophet X (2018), blending analog warmth with digital versatility, followed by the Fourm (2025), its most affordable analog synthesizer to date. In April 2021, Sequential was acquired by British audio firm plc, operating as an independent entity to continue innovating in analog and hybrid synthesis while honoring its pioneering heritage; the company marked its 50th anniversary in 2024 with celebrations of its enduring impact on .

History

1974–1980: Founding and early products

Sequential Circuits was founded in 1974 by Dave Smith, an electrical engineer and computer scientist, in his garage in , initially operating as a small-scale venture focused on developing music sequencers for synthesizers. Smith, who had purchased a synthesizer in 1972 and began experimenting with sequencing to automate musical patterns, named the company after its emphasis on sequential control devices. The operation started modestly, with Smith designing and assembling prototypes by hand to address the limitations of existing monophonic synthesizers in live performances and recordings. The company's debut product was the Model 600, an analog 16-step sequencer released in 1974, which used control voltages to drive synthesizers like the Minimoog or ARP models, enabling musicians to program repetitive patterns without manual playback. This was followed in 1975 by the Model 800, the first standalone digital hardware sequencer, featuring 16 banks of 16 steps each for storing CV/gate information in real-time or step-time modes, with playback speeds adjustable to half, normal, or double tempo; it required connection to a voltage-controlled synthesizer for sound generation but marked a significant advancement in precision and reliability over analog alternatives. In 1976, Sequential introduced the Model 700 Programmer, a digital interface that added patch memory to analog synthesizers such as the Minimoog or ARP 2600, storing up to 64 programs across eight banks with ADSR envelope controls and an integrated sequencer, allowing users to recall sounds instantly during performances. Seeking to push beyond monophonic limitations, Smith began development of an early polyphonic synthesizer prototype in 1977, which evolved into the Prophet-5. The breakthrough came in 1978 with the Prophet-5, the world's first fully programmable polyphonic analog synthesizer, offering five voices of polyphony through a architecture of dual voltage-controlled oscillators (VCOs) per voice—capable of sawtooth, triangle, pulse, and square waveforms—paired with a resonant low-pass filter (initially SSM2040 chips in Revision 1), dual ADSR envelope generators for amplitude and filter modulation, and poly-modulation routing for oscillator cross-modulation. Powered by a Z-80 microprocessor, it included a 40-preset memory system (expandable in later revisions) for storing and recalling patches, revolutionizing workflow by eliminating the need for manual knob resets between sounds. Demonstrated at the NAMM show in January 1978, the Prophet-5 shipped later that year and quickly gained acclaim in the synthesizer community for its rich, versatile analog tones, influencing artists across genres from progressive rock to electronic music. As demand grew, Sequential expanded its team, hiring key engineers including John Bowen in the late 1970s, who contributed to the 's design and preset programming, and Matt Mandell, who supported hardware and software development during the company's formative phase. This period saw initial business growth from a garage setup to a dedicated facility, with the establishing Sequential as a leader in analog synthesis innovation and driving early sales through word-of-mouth in the music technology scene.

1981–1986: MIDI development and expansion

In early 1981, Dave Smith and Chet Wood of Sequential Circuits proposed a standardized interface for synthesizers, inspired by discussions with Ikutaro Kakehashi of , to enable communication between electronic musical instruments. This initiative led to ongoing discussions throughout 1981 and 1982, including a meeting at the February 1982 . Further refinements, such as increasing MIDI channels to 16 via fax in July 1982, culminated in the finalization of the protocol by late 1982, with public announcement in November 1982. The standard was publicly demonstrated in January 1983, marking a pivotal moment for the music industry by allowing seamless integration of synthesizers, sequencers, and computers. Sequential quickly integrated MIDI into its product line, with the later receiving MIDI capabilities through a retrofit kit available from 1983, applicable to Revision 3 and earlier models. This was followed by the Prophet-600 in 1982, a more affordable six-voice successor to the featuring built-in MIDI as the first commercially available with the new standard. The Prophet-10, originally released in 1978, received updates in the early 1980s to incorporate MIDI compatibility, enhancing its dual-manual, ten-voice design for layered performances. In 1984, Sequential expanded its offerings with the Six-Trak, a compact six-voice multitimbral that supported MIDI for assigning different patches to separate channels, alongside an integrated six-track sequencer. That same year, the company launched the Drumtraks, its first digital , providing eight-voice across 13 programmable sounds and full MIDI implementation for synchronization and triggering. By 1986, Sequential introduced the Prophet VS, an eight-voice that pioneered vector synthesis by blending four digital wavetables per voice using a for real-time morphing, all controlled via . These innovations fueled the company's growth during the mid-1980s synthesizer boom, with Sequential becoming the largest U.S. manufacturer by 1981 and establishing an international presence through a European headquarters in the in 1982. The rapid expansion to larger facilities and broader distribution networks, however, began to impose financial strains amid increasing competition and production demands.

1987–2001: Closure and hiatus

In December 1987, Sequential Circuits filed for bankruptcy, marking the end of its operations as an independent synthesizer manufacturer after 13 years. The company's financial collapse stemmed from several interconnected factors, including high costs that strained its limited resources, leading to premature product releases like the to generate quick capital, which in turn caused reliability issues and eroded market confidence. Additionally, intense competition from well-funded Japanese manufacturers such as and Yamaha, who offered comparable synthesizers at lower prices, saturated the market and undercut Sequential's pricing power. An ill-fated pivot into computer audio and sound technologies around 1985–1986 further diverted resources without yielding sufficient returns, exacerbating the downturn. Following the , acquired Sequential's assets, including its , brand name, and remaining inventory, while settling outstanding debts. Despite the acquisition, Yamaha produced no new products under the Sequential name and effectively shut down the division by , leading to a period of brand dormancy with lapsed protections and no active operations. The Prophet 3000, a 16-bit sampler released in 1987, stood as Sequential's final major hardware product before the closure. During this hiatus, founder Dave Smith transitioned to consulting and development roles elsewhere in the industry. From 1987 to 1989, he led the Dave Smith Division (DSD) at Yamaha, growing frustrated with the focus on sampling over innovative sound generation. In May 1989, Smith joined Korg's team in , spearheading the creation of the Wavestation , released in 1990, which built on vector synthesis concepts from earlier Sequential work. Later, in the mid-1990s, Smith became president of Seer Systems, a company founded in 1992 that developed , the world's first professional for PCs, released in 1997 after collaborations with and Creative Labs. No evidence indicates Seer Systems was acquired by Yamaha in 1998; instead, its technology was licensed to partners like Creative Labs for integration. Throughout the 1987–2001 period, Sequential remained inactive, with its legacy preserved through Smith's ongoing contributions and early recognitions, such as his 1987 honorary membership in the for development. Smith's work during this time emphasized software and hybrid synthesis, laying groundwork for future innovations outside the Sequential banner.

2002–2014: Dave Smith Instruments era

In 2002, Dave Smith founded Dave Smith Instruments (DSI) in the , focusing on the design and manufacture of affordable hybrid analog-digital synthesizers that blended classic analog warmth with digital control features. The company's inaugural product, the Evolver, was a desktop released that same year, featuring four voices with analog oscillators, filters, and a digital effects section for versatile . DSI expanded its lineup with the Prophet '08 in 2007, an 8-voice polyphonic analog synthesizer that paid homage to Smith's earlier Prophet series while incorporating modern Curtis analog filters and digital modulation for enhanced programmability. This was followed by the Mopho in 2008, a compact monophonic analog synthesizer sharing the Prophet '08's voice architecture but optimized for affordability and portability, and the Tetra in 2009, a 4-voice polyphonic module that extended the Mopho design for multitimbral capabilities. In 2005, DSI introduced the Poly Evolver Keyboard, a 4-voice keyboard version combining the rackmount Poly Evolver's hybrid architecture with hands-on controls, emphasizing analog signal paths augmented by digital sequencing and effects. A key aspect of DSI's designs during this period was modular expandability, allowing users to link multiple units via poly-chain mode for increased ; for example, combining several Mopho or modules could create up to 8-voice setups. Accessories like the Mopho Ladder, a dedicated analog ladder filter module, further enhanced customization by integrating seamlessly with the Mopho series to add classic Moog-style filtering. These features contributed to DSI's emphasis on recapturing analog warmth in the post-digital era, appealing to musicians seeking tactile, organic tones amid the resurgence of boutique hardware. Under Smith's leadership, DSI played a pivotal role in revitalizing the boutique synthesizer market, with products distributed through major retailers such as and gaining acclaim for their build quality and innovative hybrid approach. The company's growth reflected broader industry trends toward accessible, high-fidelity analog instruments, solidifying DSI's position as a leader in independent synth design by 2014.

2015–present: Revival, rebranding, and Focusrite acquisition

In 2015, Yamaha returned the rights to the Sequential name to Dave Smith as a gesture of goodwill, allowing him to revive the brand under his company, Dave Smith Instruments (DSI). The first product to bear the Sequential branding was the Prophet-6, a six-voice launched that year, marking the beginning of the company's resurgence in the analog synth market. Shortly after, in early 2016, Sequential released the OB-6, a six-voice analog polysynth co-designed with , incorporating his signature SEM filter architecture alongside DSI's Prophet-style oscillators. By 2018, DSI fully rebranded to Sequential Circuits, solidifying the revival and aligning the company with its historical legacy. That year, Sequential introduced the Prophet X, a hybrid 16-voice combining wavetable and sample-based synthesis with analog filters, expanding the brand's offerings into digital-analog hybrids. In April 2021, British audio company plc acquired Sequential for an undisclosed sum, establishing it as a wholly owned while preserving its operational independence under Dave Smith's leadership. Smith continued guiding the company until his death in May 2022. Following the acquisition, Sequential released the Take 5 in late 2021, a compact five-voice analog polysynth aimed at accessibility and portability. In July 2025, Sequential released the Take 5 Desktop Module, a keyless version of the for tabletop use. In 2022, the Trigon-6 debuted as a six-voice featuring three oscillators per voice and an enhanced ladder filter. The company's product momentum continued into 2025 with the launch of the Fourm in September, a budget-friendly four-voice emphasizing polyphonic aftertouch and Prophet-inspired architecture. To mark its 50th anniversary in , Sequential launched an interactive online timeline chronicling key innovations from onward, alongside promotional events, customer story collections, and limited-edition releases such as the Prophet-10 Special Edition, capped at 150 units with unique lacewood paneling. As of 2025, Sequential operates from its headquarters in , , maintaining a focus on hybrid analog designs that blend vintage warmth with modern features. Integration within the Focusrite Group has fostered synergies, including software compatibility and bundled promotions with products, enhancing ecosystem connectivity for electronic music production.

Products

Prophet series synthesizers

The Prophet series, Sequential's cornerstone line of , originated with the in 1978, marking the company's breakthrough in polyphonic synthesis. This 5-voice analog instrument was the world's first fully programmable polyphonic , featuring digitally controlled analog oscillators (CEM 3340) and a multimode (SSM 2040 in early revisions), allowing users to store and recall up to 40 via a digital memory system. Its design established standards for polyphonic aftertouch and preset management in subsequent synthesizers, influencing the evolution of keyboard instruments in electronic music production. The underwent revisions through 1984, incorporating Electromusic chips in later models for improved stability, with approximately 6,000 units produced overall. A companion model, the Prophet-10, released in 1980 as a 10-voice version with dual keyboards for split and layered operation, doubling the while retaining the core architecture of two oscillators, a resonant ladder filter, and dual envelope generators per voice. In 1982, Sequential introduced the Prophet-600 as a more affordable 6-voice variant, adding connectivity for the first time in the series and using cost-reduced components like a single multimode filter per voice, though it sacrificed some of the original's preset depth. The series expanded further with the Prophet VS in 1986, a 16-voice hybrid that introduced vector modulation synthesis, blending from up to four oscillators via a joystick-controlled mixer for dynamic timbre morphing, alongside digital storage and analog filters. During the Dave Smith Instruments (DSI) era, the Prophet '08 debuted in 2007 as an 8-voice polyphonic with hybrid analog-digital architecture, incorporating onboard digital effects like reverb and delay, curved oscillators, and a 4-pole , expandable to 16 voices via module stacking. This was followed by the Prophet-12 in 2013, a 12-voice flagship with hybrid design featuring wavetable oscillators, five simultaneous types per voice, and extensive modulation matrix, supporting desktop module expansion for additional . Sequential's 2015 revival brought authentic analog recreations, starting with the Prophet-6, a 6-voice instrument emulating the original Prophet-5's '70s tone using discrete Curtis CEM 3340 oscillators and dual filters (SSM and Curtis ladder types selectable), complete with polyphonic step sequencing and vintage-mode switching for authentic signal path recreation. That same year, the OB-6 emerged from a collaboration with Tom Oberheim, offering 6-voice polyphony with dual discrete analog VCOs and signature Oberheim SEM-style multi-mode filters, plus polyphonic aftertouch and an arpeggiator for expressive performance. The series continued with the 2018 Prophet X, an 8-voice hybrid blending wavetable and FM synthesis from sample-based oscillators (150GB library included) with analog filters and effects, enabling seamless transitions between digital timbres and classic Prophet warmth, with keyboard and desktop variants supporting rackmount expansion. Across the Prophet lineage, common elements include resonant ladder filters (often Curtis or SSM designs for Moog-like response), polyphonic aftertouch in post-2015 models for nuanced control, and modular expandability through desktop modules that integrate via or CV for voice stacking. Reissues like the Rev4 and Prophet-10 from 2020 onward feature limited production runs, combining all historical revisions into a single unit with modern /USB integration while preserving construction and analog authenticity.

Other synthesizers

Sequential's early experimentation with polyphony predated the Prophet series, exemplified by the Poly-Modal Synthesizer released in 1974 as an 8-voice experimental polyphonic instrument that laid groundwork for programmable synthesis. The Pro-One, released in 1981, is a monophonic based on the architecture, featuring two oscillators, a multimode filter, and built-in 40-step sequencer and arpeggiator for performance enhancement. During the Dave Smith Instruments (DSI) era, Sequential introduced the Evolver in 2002, a desktop monophonic synthesizer employing analog modeling with two analog oscillators, two digital wavetable oscillators, twin multimode filters, and a built-in sequencer, blending hybrid analog-digital synthesis for versatile sound design. The Mopho followed in 2005 as a portable monophonic analog synthesizer featuring a classic ladder filter inspired by earlier designs, two oscillators, sub-oscillator generators for deep basses, and extensive modulation options, available in both desktop and keyboard variants with expansions like the black-panel limited edition. In 2006, the Tetra emerged as a 4-voice rackmount polyphonic synthesizer, functioning as four linked Mophos for multitimbral capabilities and a fully analog signal path, emphasizing compact polyphony for studio integration. The Poly Evolver, released in 2008, expanded this lineage with a 37-key keyboard version offering 4-voice polyphony, combining the Evolver's hybrid engine with hands-on controls and a 5-octave keyboard for performance-oriented analog modeling. The Six-Trak, introduced in 1984, is a 6-voice polyphonic and multitimbral analog synthesizer with one oscillator per voice, supporting MIDI and featuring a 6-track digital sequencer for pattern storage and playback. In the modern revival period, the Pro-2 debuted in 2014 as a paraphonic desktop synthesizer with a 37-key keyboard, featuring four oscillators including Superwaves for complex timbres, dual Curtis CEM 3340-based filters, and an arpeggiator, prioritizing hybrid synthesis in a compact form factor. The Trigon-6, introduced in 2022, provided 6-voice polyphony with three discrete voltage-controlled oscillators per voice, a multimode ladder filter, and onboard effects like analog distortion, capturing a thick, creamy analog tone reminiscent of early synth eras while supporting simultaneous waveshape selection. Sequential's Take 5, launched in 2021, offered a 5-voice compact polyphonic synthesizer with 44 mini-keys for enhanced portability, dual VCFs (including a Prophet-5 Rev4 ladder filter and a Curtis multimode), and a hybrid engine that balances accessibility with deep subtractive synthesis features. Most recently, the Fourm arrived in 2025 as an entry-level 4-voice analog polyphonic synthesizer with a 37-key keyboard supporting polyphonic aftertouch, drawing on Prophet heritage for expressive performance through integrated effects and a modern control scheme in a budget-friendly package. These non-Prophet synthesizers highlight Sequential's focus on hybrid analog-digital architectures, such as the Evolver family's wavetable integration, and accessory expandability, as seen in Mopho systems that could with Tetra units for increased . Portability remains a core emphasis, with models like the Take 5 and Fourm designed for on-the-go creation using compact keyboards and intuitive interfaces that maintain the company's legacy of innovative, voice-efficient designs.

Sequencers and drum machines

Sequential's early foray into sequencing hardware began with the Model 800, an 8-channel digital sequencer released in 1975, designed as a voltage-controlled device to interface with synthesizers like the Moog Modular and Rhodes Chroma. It featured 16 memory banks, each capable of storing up to 16 steps, allowing users to create and chain sequences for automated control of pitch, timing, and modulation. This tool marked a significant advancement in live performance and studio automation, enabling precise repetition of complex patterns without manual intervention. The Pro-One, introduced in 1981 as a monophonic , incorporated a built-in 40-step sequencer and arpeggiator to enhance its performance capabilities. The sequencer supported two independent patterns totaling up to 40 notes, with real-time recording and playback options, while the arpeggiator offered up and up/down modes for rhythmic accompaniment. These features made the Pro-One a versatile instrument for lead lines and bass sequences, integrating seamlessly with early setups following the protocol's development. In 1984, Sequential expanded into percussion with the Drumtraks, a digital drum machine utilizing 8-bit sampled sounds for 13 drum tones including kick, snare, toms, hi-hats, and . It provided 12-voice polyphony, 100 programmable patterns, and 100 songs with a total capacity of over 3,300 notes, alongside output for synchronization with other instruments. Complementing the Drumtraks was the Tom, an analog drum synthesizer released the same year, offering 6 dedicated voices for , snare, two toms, closed hi-hat, and crash , each with individual outputs and tuning controls. This pairing allowed producers to blend digital samples with analog synthesis for richer rhythm sections. The from 1984 included a 6-track digital sequencer for multitimbral sequencing across its voices. The Studio 440, released in 1987, is a hybrid device combining a 12-bit sampler, 32-voice , and sequencer with 40,000-note capacity, allowing for sample-based drum sounds and sequence editing in a rackmount format. In modern offerings like the Prophet X hybrid synthesizer, released in 2018, Sequential incorporated a polyphonic step sequencer supporting up to 64 steps and 6 notes per step, enabling layered sequences in split or stacked modes. Vintage Sequential sequencers and drum machines, including the Model 800 and Drumtraks, are now rare collectibles due to limited production runs and age-related component failures, with well-preserved units commanding high prices in the collector market. Their innovations in integration and hybrid analog-digital percussion influenced subsequent designs, such as Akai's early samplers and Roland's TR-series machines, by popularizing programmable rhythms and standardized in electronic music production.

Innovations

MIDI protocol

In October 1981, Dave Smith of Sequential Circuits and engineer Chet Wood presented a titled "Universal Synthesizer Interface" at the convention, proposing a standardized digital protocol to enable interoperability between from different manufacturers. This initiative addressed the fragmentation caused by proprietary interfaces, building on Sequential's earlier work with digitally stored presets in the , which highlighted the need for a common communication standard. The protocol, renamed Musical Instrument Digital Interface (MIDI), was refined through collaborative meetings, including discussions at the 1981 Gakki Fair in with representatives from , Yamaha, , and Kawai, leading to key adjustments such as the adoption of a 5-pin for opto-isolated transmission and a serial data rate of 31.25 kbps to ensure reliable asynchronous communication. Core specifications included support for 16 independent channels, allowing multiple devices to operate simultaneously, and fundamental message types such as note on/off events with velocity sensitivity, program change commands for selecting patches, and continuous controller messages for parameters like modulation and volume. These features prioritized simplicity and low latency over high bandwidth, facilitating real-time performance control without requiring complex hardware. Development faced significant challenges, including initial resistance from some American and European competitors at the 1982 Winter NAMM meeting, where manufacturers debated connector types (e.g., 1/4-inch jacks versus DIN) and data rates, with concerns that a universal standard might undermine proprietary advantages. Debates also centered on transitioning from analog control voltage (CV) systems—which suffered from incompatible voltage levels and polarities—to a fully digital signaling approach, ultimately favoring digital for greater precision and noise immunity. Despite these hurdles, the MIDI 1.0 specification was finalized in August 1983, incorporating expansions like System Exclusive (SysEx) messages to transmit manufacturer-specific custom data, such as patch dumps and device configurations. The first public demonstration of MIDI occurred at the January 1983 Winter , where Smith connected Sequential's Prophet-600 to 's Jupiter-6, successfully transmitting note data and controls between the instruments in real time. This milestone validated the protocol's practicality and spurred adoption. To oversee ongoing standardization, the MIDI Manufacturers Association (MMA) was formed in 1985 as a nonprofit organization, with Smith playing a pivotal leadership role in its early governance. His contributions to MIDI were recognized with a Technical Grammy Award in 2013, shared with founder Ikutaro Kakehashi, honoring the protocol's transformative impact on . Building on the original , Smith, as longtime chairman of the MMA, contributed to the development of MIDI 2.0, which was officially released on January 14, 2020. This update introduces higher resolution for controllers (32-bit vs. 7-bit), bidirectional communication, and a property exchange protocol for device discovery and configuration, while ensuring full with MIDI 1.0 devices.

Programmable polyphonic synthesis

Sequential Circuits' , released in 1978, marked a pivotal advancement in programmable polyphonic synthesis by integrating a Z-80 to enable the storage of up to 40 presets, freeing musicians from the cumbersome setups prevalent in prior modular polyphonic instruments. This innovation allowed users to save and recall complex sound configurations digitally, transforming polyphonic synthesis from a labor-intensive process into a practical, performance-ready tool. The not only managed preset storage but also handled voice assignment and calibration, ensuring consistent tuning across the five voices despite the challenges of analog voltage-controlled oscillators (VCOs). At its core, the Prophet-5's technical design employed a sophisticated voice allocation system that supported five simultaneous notes, with each voice utilizing dedicated analog circuitry—including dual VCOs, a , voltage-controlled (VCA), and envelope generators—to maintain sonic integrity while keeping production costs manageable through a fixed-architecture panel and shared digital oversight for parameter control. This approach addressed key limitations of early , such as tuning instability from temperature fluctuations in analog components, by leveraging the for automated calibration routines that stabilized pitch across voices. Dave Smith's method of integration for patch memory and voice management set a benchmark, influencing subsequent designs at competitors like ARP and , which adopted similar digital aids for preset handling and polyphonic control in their later instruments. Building on this foundation, Sequential advanced programmable polyphony with the 1980 Prophet-10, which combined dual five-voice banks into a ten-voice instrument, doubling polyphonic capacity while retaining the microprocessor-driven preset system for seamless sound layering and recall. The 1986 Prophet VS further innovated by introducing vector synthesis, where a dedicated enabled real-time mixing of up to four digital waveforms per voice from a library of 127 preset waveshapes, allowing dynamic timbral morphing programmed into memory for evolving polyphonic textures. During the Dave Smith Instruments era, the 2008 Prophet '08 refined these concepts with a hybrid analog voice engine—featuring digitally controlled analog oscillators (DCOs) for enhanced tuning stability—and an LCD interface for editing and storing 256 programs (128 factory, 128 user), expanding programmable options with multi-timbral layering and expanded modulation routing. MIDI integration later facilitated preset recall across connected devices, enhancing the ecosystem of programmable polyphony.

Legacy

Technological influence

Sequential's Prophet-5 synthesizer, introduced in 1978, established a foundational template for analog polyphonic synthesizer design by introducing fully programmable voices, stable tuning, and user-editable patches, which became benchmarks for subsequent hardware. This architecture directly influenced modern instruments such as the Moog Subsequent 37, which adopts a similar polyphonic analog signal path with dual oscillators per voice and envelope shaping to evoke the Prophet-5's warm, versatile tonality, and the Arturia PolyBrute, a 6-voice hybrid that builds on the Prophet's polyphonic framework while incorporating matrix modulation reminiscent of early programmable polys. The Prophet-5's Curtis Electro-Music (CEM) filter designs, particularly the CEM3320 voltage-controlled filter, have been emulated in hardware and software for over four decades, shaping the sonic character of countless synthesizers through their smooth resonance and low-end response. Dave Smith Instruments (DSI), Sequential's predecessor in the modern era, pioneered hybrid analog-digital synthesis with instruments like the Evolver (2002) and Prophet-12 (2013), blending oscillators and filters with digital wavetables and processing to expand sonic possibilities without sacrificing analog warmth. This fusion influenced contemporary designs such as the UDO Super 6, a 12-voice binaural hybrid that combines analog VCOs with digital effects and , echoing DSI's approach to integrating digital control for enhanced and modulation. Similarly, Modal Electronics' hybrid offerings, including the Argon8's wavetable engine paired with filtering, reflect DSI's legacy of bridging paths with digital flexibility to create expansive, modern textures. The 2015 collaboration between Sequential and on the OB-6 revived the classic SEM (Synthesizer Expander Module) filter topology, inspiring a wave of retro-analog revivals in the industry. This design prompted Behringer's UB-Xa (2023), a 16-voice polyphonic emulation of the that incorporates SEM-inspired filters for authentic '70s Oberheim timbres, and influenced Korg's analog modeling in synths like the , which draws on vintage polyphonic circuits for its multi-engine architecture. Following Dave Smith's death in 2022, Focusrite's ownership—established via the 2021 acquisition—has ensured operational continuity, with the company maintaining Sequential's design philosophy through independent product development led by Smith's original team. This stewardship culminated in 2024's 50th anniversary Prophet-10 Special Edition, featuring custom lacewood paneling and authentic Rev1-3 circuit emulations to honor the brand's hardware heritage, and continued into 2025 with the release of the affordable Fourm four-voice in September and a November OS update for the Take 5 enabling 10-voice polyphony via Poly Chain. The protocol, co-developed by Smith in 1983, remains integral to nearly all electronic musical instruments, enabling interoperability across over a billion devices worldwide and forming the backbone of hardware-software integration in ecosystems. Prophet-5-inspired emulations persist in software, such as u-he's Repro-5 plugin, which models the original's CEM filters and polyphonic architecture for precise replication in workstations. Smith's contributions earned him the 2005 TECnology Hall of Fame induction for and the 2013 Technical Grammy Award shared with Ikutaro Kakehashi.

Cultural and industry impact

Sequential's synthesizers, particularly the , have left an indelible mark on through their prominent use in landmark recordings. The provided the iconic in Rush's 1981 hit "," crafted by bassist to blend analog warmth with progressive rock's technical precision. Similarly, Kraftwerk incorporated the into their later works, such as the 1981 album , enhancing their pioneering electronic soundscapes with polyphonic capabilities that defined krautrock's evolution into . The Drumtraks drum machine also influenced early electronic genres, appearing in tracks by artists like Prince on 1999 (1982), where its sampled acoustic drums added a punchy, realistic groove to funk and emerging . Notable artists across generations have championed Sequential's instruments, amplifying their cultural resonance. utilized the for the ethereal textures in "" from (2000), showcasing its versatility in . ' and composer have frequently employed Prophet models in industrial and film scores, highlighting the synth's enduring appeal in high-profile productions. These endorsements extend to , where modern producers draw on Sequential's analog heritage to infuse tracks with vintage timbre amid digital workflows. The company's innovations, including co-inventing the protocol, facilitated seismic shifts in music production by standardizing hardware-software integration, paving the way for digital audio workstations like . This interoperability democratized music creation, enabling seamless sequencing and control that transformed studios from hardware-centric to hybrid environments. Sequential's post-2015 revival as a boutique operation under Dave Smith's leadership inspired a wave of startups, mirroring the resurgence and fueling the 2010s hardware renaissance. Economically, Sequential contributed to the synthesizer boom, with the selling approximately 6,500 units and helping propel the global market toward multimillion-dollar scales dominated by hits like Yamaha's DX7. The 2021 acquisition by plc for approximately $20 million underscored Sequential's lasting value, integrating its legacy into a broader audio ecosystem. Culturally, the company's 50th anniversary in 2024 featured commemorative events and retrospectives, celebrating its foundational role in electronic music from to EDM.

References

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