Intro to Synthesis, Parts 1 and 2: Oscillators and Other Building Blocks

Intro To Synthesis is a new, six-part video series by us here at Reverb that promises to lead anyone interested in synths through the foundational building blocks of the instruments. Whether you’re a true beginner or an experienced enthusiast, this series is sure to give you a deeper understanding of all of the basic concepts.

Today, we’re beginning with the starting point of any synthesizer’s sound—oscillators, or the generators that create the raw sound the rest of your synth’s features will modify.

In the first video above, Reverb’s Justin DeLay begins by explaining the various sound waves oscillators generate, demonstrating each of his Korg Mono/Poly.

A saw wave or sawtooth wave is a bright, exciting waveform that, as Justin explains, "It’s really, really great for synthesizing sounds like strings, where you really want to get some of that energy and excitement in the upper range."

A square wave is a bold, harmonically rich waveform that has a rounder, more vocal or reedy timbre. Because of its harmonic complexity, there are a lot of frequencies present to be shaped by further processing.

Meanwhile, a triangle wave is a duller sound that, by nature of having a thinner, less lively waveform, is great for bass or muted keyboard tones.

Sawtooth Wave
Square Wave
Triangle Wave

The final waveform Justin explains is noise. By itself, this will sound just like TV static, but when blended with other oscillator waveforms, it can add harmonic complexity and energy to their sounds.

In the second part of Justin’s exploration of oscillators, he shows you how to take the raw sound of the generators and start to give them different shapes and characters with other parts of the synth.

"The cool thing about a square wave is it doesn’t just have to be a square," he says. "It can be a square all the way down to a narrow pulse. And every variation in between will give you a different sound."

Pulse Width

Through pulse width modulation, you can change the sound of the square wave, bringing out different tonal characteristics as you make it thicker or thinner. You can do this manually on some synths, as Justin demonstrates, or through automation, which we’ll explore later in the video.

Because many synthesizers include more than one oscillator, you can stack them on top of each other "to make a bigger, more harmonically interesting sound."

The octave or range function of an oscillator allows you to choose the frequency range played by the oscillator. So when using multiple oscillators, you can set one to, say, the bass range and others to higher ranges to separate the sounds as if they were individual members of an ensemble.

For those who might be confused about why their range or scale knob includes numbers like 32’, 16’, 8’, and 4’, Justin explains that this is a holdover from the time of pipe organs, where the actual length of the pipe would determine how low or high the notes would be.

In addition to changing octaves, you can also fine-tune an oscillator’s note with the tune knob. Slightly detuning one oscillator in the same range as another, will introduce a beating, pulsating pattern similar to guitar strings just barely out-of-tune.

Modulation is a major concept necessary to understanding synthesis. It involves taking the signal from one area of a synth and using that output to change another signal, without needing to manually turn a knob.

As just one example of this concept, Justin sends an LFO, or low-frequency oscillator, to the synth’s pulse-width knob to introduce a varying width to the pulse wave (as demonstrated manually earlier in the video). In addition to changing the shape of the square wave, you can also use an LFO to modulate the pitch.

With the foundation set in these two videos, we’re going to be exploring all of the various ways you can add character to your synthesized sounds through filters and more features in the coming episodes. Be sure to check back next week for the third part of our series.

Full Intro to Synthesis Series
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