Synthesizer Fundamentals

Glenn Poorman, June 2011
Updated from an article originally written in June, 2008.



Contents

Introduction

My interest in synthesizers goes back to the early 70s. As a very young music student, I was paired with a local high school student for lessons and I ended up studying with her for several years. Her musical tastes and knowledge of genres covered a lot of ground and she regularly opened my eyes to things well outside my narrow field of vision including the world of synthesizers. We would listen to the Beach Boys and talk about the use of the Theremin. We listened to Henry Mancini and talked about the synthesizers he used in the TV themes for "The Mystery Movie" and for "Cade's County". We talked about the work of Wendy Carlos and the instruments built by Bob Moog. We talked about the ARP units that fueled some of Pete Townsend's work as well as Edgar Winter's "Frankenstein".

In 1979, I managed to briefly put my hands on a real synthesizer while attending the Summer Arts Camp at Interlochen. The instrument was made 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 the Roland Juno-60. By then I was recording my own music and the 121normal studio was in its second location. I had the Juno-60 for the better part of three years and used it in several of the recordings from that era.

In spite of all the time I put into the Juno-60, I still never really understood how it all worked. I just tweaked knobs and sliders until I got the sounds I liked. I was able to save the sounds in memory so I wouldn't have to repeat my hunt and peck process every time I fired it up. After a while, I simply became good at remembering what the various sliders did even if I didn't really know why they did it (turn that doohickey over there so the note makes that "dwap" sound).

After taking a brief hiatus in the late 80s, analog synthesizers made a huge comeback during the 90s. As we moved into the 21st century, computers took over and the newest synthesizers came in the form of software. While the heart of today's software synth works very much like its hardware ancestors, the almost unmeasurable amount of additional control makes that hunt and peck method of creating sounds that served me so well on the Juno-60 virtually impossible today. There are simply too many variables. For many hobbyists, this isn't necessarily a problem as both modern hardware and software synths come with enough presets to keep the average user busy for the life of the synth. If you want to go off and create your own sounds though, a basic understanding of sound synthesis has become an absolute must.

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. An electronic music synthesizer provides components to simulate the various aspects of sound and then those components are combined to produce what we finally hear.

There are several methods of synthesis used in both hardware and software units including subtractive synthesis, additive synthesis, frequency modulation synthesis (also called FM synthesis), wavetable synthesis, and sample based synthesis (just to name a few). Many of today's units, especially the software units, will combine several methods of synthesis allowing the user to choose the method they want to use. For our purposes, we'll focus on subtractive synthesis as this method was used by the original units of the 60s and tends to be the most popular (and easiest to understand).

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. It's also a very human-centric definition as we know that other members of animal kingdom are capable of detecting sounds well outside the range of 20 to 20,000 hertz and that many instruments generate frequencies outside of that range as well. For our purposes though, the heart of that definition works.

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 the original analog synthesizers, these components were all voltage controlled and were frequently referred to as the VCO (voltage controlled oscillator), VCF (voltage controlled filter), and VCA (voltage controlled amplifier). It's not uncommon to see the old acronyms still in use today even on units that are no longer voltage controlled.

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

A Better (Subtractive) Synthesizer

The basic synthesizer from the previous section, while a useful 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. There has never been a single commercially available synthesizer, however, that didn't come with some extra bells and whistles to color up the tone and make it a bit more interesting.

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.

Software

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.

Conclusion

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, 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!