Synthesis Made Simple: Part 2 - Oscillators - Meet the Waveforms

Now for the first in what will undoubtedly be many half-baked analogies. Imagine you’re decorating a cake. The cake itself has already been baked and cooled. It’s just your responsibility to decorate it. At your disposal, you’ve got different flavors of frosting, sprinkles, nuts, pieces of fruit, whipped cream, and –what the hell – even some mustard and pickles. You can combine these ingredients into many different combinations, each of which can yield an entirely different-tasting cake.

In this scenario, the pre-decorated cake is a good representation of the OSCILLATOR’S role in synthesis. The oscillator is your starting point - your blank slate. Put simply, an oscillator is a sound generator. It might generate a simple audio waveform, it might play back a sampled waveform, it might even be a bunch of waveforms chained together in a wavetable, but in all those cases the oscillator’s job is to make the raw sound. You then use other parts of the synthesizer (like the cake decorations) to take that basic beginning sound and mold it into any of literally hundreds of thousands of different sounds (different-tasting cakes).

It’s worth noting something you’ll probably notice pretty quickly after playing around with different synthesizers. Manufacturers are really fond of giving different names to things that are essentially the same. So you may see an oscillator called a generator, VCO, a DCO, a source, a voice (confusing since this can also refer to polyphony), or any number of other terms. It’s true that most contemporary synths don’t produce their sounds via “true”, physical oscillators, but “oscillator” is the generally accepted generic term for an individual sound generator in a synth. Don’t let the terminology throw you off too much. Oscillators are generally easy to recognize no matter what goofy name the manufacturer decides to slap it with.

Now, if all oscillators output the exact same sound, it would be pretty boring, so almost all oscillators have multiple ‘flavors’ of sound called WAVEFORMS. On a classic analog synth, these waveforms are named for the shape of a single cycle when you view it on an oscilloscope. They are the SAWTOOTH wave, the SQUARE (or PULSE) wave, the TRIANGLE wave, and the SINE wave. As synth technology advanced, sampled digital waveforms became more common, and this basic line-up of waveforms expanded significantly, sometimes into the hundreds or even thousands of available waveforms. But we’re keeping things simple here, so let’s just stick with the ‘classics’ for now.

The SAWTOOTH waveform has a bright, buzzy, harmonically rich sound. It’s one of the ‘thicker’ sounding waveforms and is great for brass, strings, leads, pads, bass, and honestly, just about anything. It’s a good ‘utility’ waveform and one you’ll probably use a lot. This is what a single sawtooth wave sounds like:

A SQUARE waveform (also known as a PULSE waveform) is bright-sounding too, but has a more harmonically simple, “hollow” sound. It’s good for bells, basses (in techno & house music especially), organs, flutes, etc. This is what a single square wave sounds like:

Many synths offer an additional control for their SQUARE/PULSE wave known as PULSE WIDTH MODULATION. It allows fatter, more harmonically complex sounds from a single oscillator by stretching and compressing the “width” of the pulse wave in real time. This can be great for emulating sounds like guitars or evolving pads/leads, but these days is probably most commonly heard being used for those fat trance leads the kids like so damn much. Here is what it sounds like:

The TRIANGLE waveform is a much mellower, delicate -sounding waveform. Sonically, it sits somewhere in between the sound of a SQUARE and a SINE wave. It’s great for subdued pads, mellow electric pianos, soft bells, flutes, and other sounds on the more laid-back end of the spectrum. Here’s what a single TRIANGLE wave sounds like:

The SINE waveform is the simplest wave possible harmonically speaking, as it consists only of a single harmonic. As you might expect, this is even mellower than a TRIANGLE wave and is also good for soft sounds. It’s also commonly used for sub bass type sounds and many basic types of synth drum and percussion sounds. Here is what a single sine wave sounds like:

I can already hear you saying, “But Tom, you handsome devil, these sound so thin and wimpy. Surely that thunderous synth bass on the latest club hit wasn’t simply made with these?!” Well, of course it is a bit more complicated than that, so next time, we’ll talk about the use of multiple oscillators for thicker, more complex sounds.