My name is Henry Birdseye and I love modular synthesizers. They have been my interest and my passion ever since I heard the classical record “Switched-on Bach.” The most popular classical recording of all time, “S-O-B” demonstrated that synthesizers could be played to make “real” music, and not a bunch of bloopy beepy sounds.
This “real” approach to electronic music was called “East Coast,” because the machine on the cover was invented by Robert Moog in New York state. Across the country, at about the same time, 1965 or so, Don Buchla wanted to make a synthesizer that redefined music altogether… bloopy beepy sounds allowed. This “West Coast” music was championed by such fellows as Morton Subotnick on his “Silver Apples of the Moon.” The Moog and the Buchla synthesizers were “modular,” meaning that users could buy modules according to their needs. Some modules generated sounds, others modified sounds, still others generated voltages used to control pitches and durations. They were “voltage controlled.”
But, the Moogs and the Buchlas were not compatible. They used differing standards for their control voltages. The Buchla synthesizers didn’t even have traditional keyboard controllers.
And in 1960’s money, these things were expensive! Due to the high cost, $10,000 to $50,000 for a completed system, very few private individuals owned one. The main customers at the time were universities, recording studios and a few musical groups.
In time, more inventors created new synthesizer designs and new types of modules, and an industry was born.
So, what were these monsters actually doing, you ask? Modules were interconnected with cables and sounds and control voltages made sonic changes to other modules resulting in a “patch.” Patches could be extremely simple or devilishly complex.
All of this relates to the nature of sound. Everything you hear can be broken into a spectrum of sine waves. A single sine wave sounds as a single pitch, it has no harmonics, or overtones.
Modules called “oscillators” generate waveforms, and control voltages would control their pitch.
The more complex the waveform from these oscillators, the more harmonics. These VCO’s (voltage controlled oscillators) usually output a variety of different waveforms, each with different harmonics.
In this graph, we’re looking at the spectrum of sound for a few waveforms. The large spike on the left is the fundamental frequency, and the harmonics fall off in amplitude as they increase in frequency. The top waveform, for example, is called a triangle wave. Above the fundamental (f), there are harmonics at three times the frequency of the fundamental (3*f), 5*f, 7*f, 9*f and so on to infinity. Human ears cannot detect frequencies above about 20,000 cycles per second. The second waveform is a square wave, very easy to make electronically. Third is a sawtooth wave, with more harmonics than a square wave, and the bottom one is a pulse wave with a similar harmonic profile to a sawtooth, but a different sound.
A simple patch
The simplest patch would be a keyboard sending its pitch control voltage to a VCO and the VCO connected to a speaker. This would be a very boring sound. First off, oscillators are always on. Playing the keyboard would certainly change the pitch of our sound, but it always be there. We wouldn’t know when a note begins or ends.
Adding Complexity to the Patch
Keyboards don’t just send out pitch control voltages. They can also send out a signal called a gate, that’s on (5 to 10 volts) when we press a key, and zero volts when we let go. Here’s a patch using a VCA, voltage controlled amplifier to shape the sound, turning it on and off, a couple Envelope Generators that output voltages to the VCA and to a VCF, a voltage controlled filter, whose job is to remove some of those harmonics from the oscillators.
In this patch, touching a key on our keyboard makes a few things happen all at once.
- the pitch CV changes the pitch on two VCOs (for a rich full sound) The two VCOs are mixed and sent to a Voltage Controlled Filter.
- The keyboard sends a gate as long as we hold down a key. That gate is fed to two envelope generators, that reshape that gate into a slow signal that controls the cutoff of the filter and a signal that opens up and turns off the Voltage Controlled Amplifier.
- The output from the VCF goes into the VCA.
Over the past 50+ years, circuit designers have come up with many hundreds of different modules, and integrating digital technology has allowed prices to fall and features to grow.
The modular synthesizer community has grown to thousands, if not tens of thousands, of users across the globe.