Synth-A-What?

            To help everybody better understand synthesis, I am going to break it down into sections. Synthesis is the building up or combining of different elements to create a NEW whole. Now what does that mean? Nothing, not without some context. There are many forms of synthesis including Subtractive, Additive, FM, Granular, Wavetable, and so on and so on. But how are these forms any different from one another? It all comes down to the internal components and its overall construction, but the important thing to remember is they all have one goal, to create a NEW sound.

The panel on the analog Arp Odyssey, a
subtractive synthesizer, clearly shows
the subtractive synthesis chain. Every
section of the subtractive process is in order:
VCO, VCF, then VCA. There are some
other sections in between, but for now we
will only focus on those sections.

            The easiest form of synthesis to explain, and the first type of synthesis I learned about from my repair job at A Sound Education, is Subtractive synthesis. There are there distinct sections of subtractive synthesis, a VCO, a VCF, and a VCA. The VC in each of the three stands for Voltage Controlled, and the letters after describe the section of the synthesizer (Oscillator, Filter, and Amplifier).  Everything in old analog Subtractive synthesizers was Voltage Controlled meaning that the parameters are changed or altered by an applied voltage. This variable voltage allows for changes in pitch, a sweeping cutoff on a filter, or any other parameter change.

            In Subtractive synthesis, an audio signal stemming from the VCO, usually a complex waveform (but sine waves are also present) such as a Square, Sawtooth, Triangle wave, or any other sound rich in harmonics/ partials is sent to the VCF where its harmonics are attenuated or taken away to create a more diverse, altered timbre.

I’ll ask the question (because I know you’re dying to ask it); how is taking away harmonics synthesis, when you clearly stated synthesis is the building up or combining of different elements? Well to you I say, read the second sentence again and look at the bolded all capital word. The most important part of synthesis to understand is it is the creation of something new. By filtering away harmonics, you are able to make a more useful sound; instead of something that might normally have been present in the whole audio spectrum with all its harmonics, and taking up valuable space in the mix, you can now filter it out and make it fit where you want.

Once the original audio from the oscillator has been sent through the filter, it reaches the amplifier, or the VCA, and boosts the signal so we can all enjoy it (or cringe, you’re in control).

That is the basic run through of Subtractive synthesis. In subsequent posts I will detail further about the parameters and functions of the VCO, VCF, and VCA, but I feel that is enough to wrap your brain around for the moment. A note to end on; synthesis does not need to thought of as coming from a dedicated “synthesizer”, but can be anything from the graphic equalizer in iTunes, to a guitar pedal. As long as you are changing the original sound and creating something new, you are synthesizing.

Basic block diagram of subtractive synthesis.
VCO to VCF to VCA.

...My mistake in "Player Piano" was my failure as a futurist. I did not foresee transistors, and so imagined that super computers would have to be huge, with bulky vacuum tubes taking up a lot of space. -Kurt Vonnegut in "Letters"