Synthesizer Fundamentals

Glenn Poorman, September 2022
Original written in June, 2008.
Updated in June, 2011 and again in August, 2022.



My love for synthesizers goes back to the early 70s, Henry Mancini, and a music teacher I had who regularly opened my eyes and ears to things outside my narrow field of vision. One evening I sat mesmerized listening to the opening music for the "NBC Mystery Movie" written and performed by Mancini. I brought it up at my next lesson and my teacher pulled out a Mancini record featuring the very same music along with the opening theme for another show called "Cade's County". She went on to explain the synthesizer and the popular units at the time made by Moog and ARP. From there I was off in discovery mode. Wendy Carlos, The Who, ELP, Edgar Winter. There were a lot of cool recordings being made using synthesizers and I'd felt like a door had been opened. [1]

In 1979, I managed to briefly put my hands on a real synthesizer while attending the Summer Arts Camp at Interlochen. The instrument was a Mini-Korg sold by Univox. I was in the high school jazz ensemble that summer and our instructor brought the instrument along to loan to our piano player. For most of us this was a first so we were understandably anxious to give it a try. Then in 1984, I came into possession of a Roland Juno-60. By then I was recording my own music and the 121normal studio was in its second location. I had that first Juno-60 for the better part of three years and used it in several of the recordings I made during that time. In those early years I never really understood how it all worked though. I just tweaked knobs and sliders until I got sounds I liked and became good at remembering what the various sliders did even if I didn't really know why they did it.

After a bit of a hiatus while the world went digital, analog units started making a comeback during the 90s. While the basic building blocks of the new analog units were the same as their ancestors from the 70s, manufacturers now had the luxury of marrying old and new technology providing more functionality than had been available before. Furthermore, the rise of computers and the DAW saw the introduction of software based synthesizers and "virtual analog" units which were digital reproductions of analog units. With all the additions, it was becoming harder and harder to hunt and peck your way around a synthesizer so I back tracked and made a concerted effort to learn how it all worked.

That brings us here. As I tend to do when learning things like this, I started writing it all down and my aim here is to present the basics. While every manufacturer does things just a little bit differently, they're all built on the same foundation and if you can get a good understanding of that foundation, you should be able to navigate the rest.

So what is a synthesizer? By its very definition, a synthesizer is something that produces by synthesis or by combining parts to form a whole. A music synthesizer provides components to simulate the various aspects of sound and then those components are combined to produce what we finally hear. Today there are several methods of synthesis used in both hardware and software synthesizers. The earliest and still the most popular method (and easiest to understand) is subtractive synthesis which is what we'll focus on here. So before we break down the basic components of a subtractive synthesizer, let's break down the components of sound.

Sound (simple version)

Of the many definitions of the word sound in the American Heritage Dictionary of the English Language, the first reads as follows:
vibrations transmitted through an elastic solid or a liquid or gas, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being detected by human organs of hearing.
That's a fairly cold definition for something that can be so moving when it comes in the form of music. In musical terms, a sound is essentially made up of three components.

The Basic (Subtractive) Synthesizer

In simplest terms, subtractive synthesis subtracts harmonic content from a sound by passing that sound through an audio filter. The basic subtractive synthesizer is generally broken up into three sections corresponding directly with the three basic components of sound. Those three sections are the oscillator (pitch), the filter (timbre), and the amplifier (loudness). On an analog synthesizer, these components are all voltage controlled and are frequently referred to as the VCO (voltage controlled oscillator), VCF (voltage controlled filter), and VCA (voltage controlled amplifier). It's not uncommon to see those acronyms in use on units that are not voltage controlled or are simulated in software just because they've become so engrained in the nomenclature.

Let's take a look at what would be the world's simplest and most basic subtractive synthesizer and then discuss the sections in greater detail.

Figure 1. The most basic synthesizer

Adding Color

The basic synthesizer from the previous section, while semi-useful as a teaching tool, isn't much good for anything else. Only the most basic tones are possible and the character of those tones is fairly cold. Even the cheapest and most basic commercially available synthesizer is going to come with at least two additional components for adding a little color and warmth to your sound. Those components are an envelope generator (to modify the sounds initial attack and decay) and a low frequency oscillator for adding modulation (vibrato) to the sound.

Figure 4. A better synthesizer

More Sound Sources

The synthesizer shown back in figure 4 provides enough of the tools to be sold commercially. Many units currently on the market provide as much or little more than that one does. Pair that up with some additional effects units, some nice delays, some lush reverbs, and you have enough to make some really cool music. There are always more extras that can be added though and the first extras provided by many units are additional sound sources which usually come in the form of additional oscillators and/or a noise generator.

Figure 6. Synthesizer with more sound sources

More Bells and Whistles

What we've looked at so far could be considered the bare essentials. These are the components that a synthesizer would be useless without. Most (if not all) units will provide some other bells and whistles though to make the unit more interesting and more musical. The added components vary and there's no way to cover all of them but we can touch on some of the more common additions.

How Some Classic Units Worked

Synthesizers have been commercially available since the 60s. Ever since the very first units hit the scene, the trick as a manufacturer has always been to provide the customer with all of the control that makes these units so powerful but present that control in such a way that can be easily learned and understood. For the most part I believe they succeeded. But to really get the most out of any synth unit (either then or now) you still need to know the basics. Let's take a quick overview at some of the classic synths that have existed over the years and how they map back to the components discussed here.


Today, software synthesizers are everywhere. These are synthesizers that come in the form of software for your computer. These programs can be used as stand alone synthesizers allowing you to generate the tones via a MIDI keyboard controller (or any other kind of MIDI controller). The same programs can also be used as plug-ins for your favorite DAW software allowing MIDI tracks to be recorded and then assigned to the synthesizer plug-in for playback. They are a revolution and keeping track of them all is virtually impossible. Many of these synths are, at their heart, subtractive synthesizers simulated via software. Many are a combination of different kinds of synthesizers including but not limitied to subtractive synths.


I loved synths when I first learned of them and have really never stopped. They allow you to continuously go beyond traditional sounds in music and create new ones. With the proliferation of software synths and Eurorack[2], more people than ever have access. For the most part, you can have a lot of fun picking apart the presets and experimenting in the dark. A good grasp of how synths work, however, will go a long way toward making your musical visions become reality. Armed with a little knowledge, you can not only create the sounds you want to create but you can also look at how some of those presets were created and say "aha ... THAT's how they did that". As with most things in life, a little knowledge can go a long way.

Most of all though ... it's fun! Lots and lots of fun!

[1] Later I would find out that the Mystery Movie theme was, in fact, not played on a synthesizer but was played by jazz pianist Clare Fischer on a Yamaha YC-30 combo organ.

[2] Eurorack is a modular synthesizer format originally specified in 1996 that has become the dominant hardware modular synthesizer format in the world today.