Author: Jooyoung Kim

Hello! This is Jooyoung Kim, an audio engineer and music producer. Today, I’ll begin a new article series, Advanced Synthesizers & Gear.

In this series, we’ll talk about the history of modular synthesizers and the equipment. Also, we’ll figure out why famous synthesizers became so popular and how they work.

Before we focus on these topics, we need to know about the history of synths and how electricity can be turned into sound.

Let’s dive in!

Harald Bode

Harald bode, a German engineer and physicist(as a physics major myself, I feel a deep sense of kinship with Harald Bode), was a pioneer of the synthesizer.

He started a recording business, but soon ran into a major obstacle: the grand piano. At the time, recording technology was in its infancy compared to today, making it incredibly difficult to capture the true depth of the instrument.

Driven by this limitation, his inner physicist took over. Instead of trying to perfect the replication of acoustic instruments, he envisioned a completely new path—creating musical sounds 100% out of electronics using vacuum tubes. Guided by the physical principle that human voice timbres (Klangfarben) change based on the intensity of overtones, he laid the very foundation of modern synthesis by designing a system where parameters could be shaped with half-rotary knobs.

For those interested in exploring his technical blueprints and concepts firsthand, please look for his seminal 1961 publications: ‘European Electronic Music Instrument Design’ in the Journal of the Audio Engineering Society, and ‘Sound Synthesizer Creates New Musical Effects’ in Electronics magazine. Also you can see the bode’s equipment in eContact.

His groundbreaking concept of using voltage control to adjust parameters quickly spread through the pioneer community, deeply inspiring the figures who would go on to invent the world’s most iconic synthesizers: Robert Moog and Don Buchla.

Robert Moog

Robert Moog also majored in Physics during his undergraduate years, earning his Bachelor of Science from Queens College in 1955 before completing a PhD in Engineering Physics at Cornell University. With this background, Moog approached electronic music through a technological lens very similar to Harald Bode’s.

In the fall of 1960, at the Audio Engineering Society (AES) convention in New York, Moog attended Harald Bode’s presentation of his modular ‘Audio System Synthesizer’. At this convention, Bode demonstrated the concept of using voltage control to manipulate audio parameters within a modular architecture.

Following this exposure to Bode’s design, Moog set out to develop a compact, practical synthesizer for musicians, contrasting with the room-sized systems of the era like the RCA Mark II. While previous instruments relied on hundreds of vacuum tubes, Moog utilized newly available silicon transistors, leveraging the exponential relationship between input voltage and output current.

This application of transistor physics led to his principal innovation in 1964: the Voltage-Controlled Oscillator (VCO). While Bode established the foundational concept of altering parameters via voltage, Moog engineered the precise circuitry that mapped input voltage to specific musical intervals. Through this hardware, Moog standardized fundamental synthesizer concepts, including modularity, envelope generation, and the pitch wheel.

Moog viewed his role primarily as a toolmaker for artists rather than a corporate businessman, choosing not to patent core innovations like modularity or voltage control.

Don Buchla

Interestingly, the application of physics to modular synthesis was not confined to Harald Bode and Robert Moog. Donald Buchla, another pioneer who co-invented the voltage-controlled modular synthesizer independently during the early 1960s, also graduated as a physics major from the University of California, Berkeley, in 1959.

In 1962, Buchla formed his company, Buchla and Associates, in Berkeley. He was commissioned by composers Morton Subotnick and Ramon Sender of the San Francisco Tape Music Center to create an electronic instrument tailored for live performance. Guided by this request, Buchla began designing his first modules in 1963.

While Robert Moog was developing his system on the East Coast, Buchla was working independently on the West Coast. In 1965, utilizing a grant from the Rockefeller Foundation, he assembled these modules into the Buchla Modular Electronic Music System (later known as the Series 100), which entered commercial production in 1966.

Like Moog, Buchla utilized voltage control as the core mechanism to alter audio parameters. However, his approach to user interfaces and musical philosophy differed significantly. While Moog standardized the traditional piano-style keyboard to make the instrument accessible to conventional musicians, Buchla deliberately rejected the keyboard, viewing it as a limitation carried over from acoustic history. Instead, he pioneered alternative control interfaces, such as touch-sensitive plates that allowed for non-traditional, expressive manipulation of voltage.

Because these two distinct styles of synthesizers were developed independently based on the geographical regions where their creators worked, Moog’s system became known as the East Coast style, while Buchla’s was termed the West Coast style.

Doepfer

The historical lineage of physics-driven modular synthesis culminated in the late 20th century with the establishment of the Eurorack standard. Developed in 1995 by Dieter Doepfer, the founder of Doepfer Musikelektronik, Eurorack solved a critical fragmentation problem in the modular synthesizer market. Like Bode, Moog, and Buchla before him, Doepfer formally studied physics, beginning his academic training at Munich in 1972.

Doepfer’s entry into hardware development was directly influenced by his background in physics. While completing his mandatory community service in the ophthalmology department of a Munich hospital, Doepfer utilized the department’s dedicated electronics laboratory—originally built for laser eye surgery research—to quietly develop his earliest synthesizer circuits. This research resulted in his first complete system, the Polyphonic Module System (PMS), released as a DIY kit.

Throughout the 1980s, Doepfer continued to expand his technical expertise. He integrated specialized integrated circuits (ICs) from Curtis Electronic Music Specialties (CEM) to build highly efficient analog systems, and later adapted to the digital transition by developing 8-bit sampler cards and MIDI master keyboards. However, the commercial market shifted during the 1990s; a resurgence of interest in analog synthesis led to the unexpected success of his MS-404 monophonic synthesizer in 1994, which prompted high demand for expanded modular options.

To address this demand systematically, Doepfer introduced the A-100 system in 1995, establishing the Eurorack format. Prior to this, systems by Moog or Buchla used incompatible dimensions and electrical standards. Doepfer unified the ecosystem by introducing open, standardized physical and electrical specifications:

• Physical Dimensions: Height was set using the sub-rack unit standard at 3U (approx. 128.5 mm), and width was measured in HP (Horizontal Pitch), where 1 HP equals 0.2 inches (5.08 mm).
• Electrical Connectivity: Power was distributed via standardized ribbon cables supplying ±12V DC.
• Signal Interface: Control Voltages (CV) were routed using compact 3.5mm mini-jacks rather than the bulky 1/4-inch or banana jacks of earlier decades.

By keeping this format open, Doepfer created a universal framework that allowed third-party manufacturers and boutique designers to build compatible components. His designs even attracted pioneers of the genre; Florian Schneider of Kraftwerk collaborated with Doepfer to modify hardware for speech synthesis triggering, a relationship that later influenced the development of the MAQ 16/3 MIDI analog sequencer.

Through these modular standards, Eurorack transformed synthesis from a market of isolated, proprietary hardware into a decentralized, global ecosystem.

Furthermore, because this standard has become so widespread, even non-Eurorack standalone hardware instruments often feature compatible 3.5mm patching connectors. Thanks to this universal connectivity, users can cross-connect entirely different, independent synthesizers to act as interlinked sub-components—such as routing one synthesizer’s output to serve purely as an oscillator, bypassing into another instrument’s filter, or patching through separate external units for saturation and effects.

I will explain the technical details and creative mechanics of these Eurorack modular synthesizers in a later post.

See you then!