Synths don’t need to be complex things. Classic instruments such as Roland’s Juno-6 or SH-101, or even the Minimoog Model D, are all fairly straightforward instruments, comprised of a simple combination of oscillators, filters and modulators that most users could get to grips with after a few simple tutorials and a couple of hours of experimentation.
In 2023 though, technology has opened multiple new avenues for sound design. Synths are getting more complex, both in the hardware and software realms. While the classic setup of those analogue instruments still provides the cornerstone of a lot of modern instrument designs, it’s common for even budget-friendly synths to add in additional complexity, through advanced features or expanded options. While a basic understanding of oscillators and filters will still get you going, it won’t be long before newbie synthesists encounter more advanced and alien concepts like audio rate modulation, logic-based processors or CV patch points.
It’s these realms we want to delve into this issue. Seeing as you’re reading FM, we’re going to assume a basic level of knowledge. Let’s skip over the basics of how to program a simple synth patch, and instead explore the more advanced elements of synth design: what’s the difference between an ‘East Coast’ and ‘West Coast’ synth? What can digital synthesis do that analogue can’t? How can a semi-modular patchbay expand a synth’s sound? What do tools such as ‘sample & hold’, ‘attenuators’ or ‘low pass gates’ do?
One note before we get started – we’re aiming to offer an explainer to a grab-bag of synthesiser concepts in these pages, but since all instruments are different, we’ve no hope of being truly definitive. While we hope to give you a grounding in some of these concepts, if you really want to master a specific synth, the best thing you can do is read the manual, test out each individual element and get a feel for how each feature affects the sound.
OSCILL ATOR SHAPING – BE YOND SINES AND SQUARES
>Synthesisers come in many shapes and sizes, but for the most part they share a few fundamental similarities. All synths start with some kind of sound generator, usually called an oscillator, the raw sound of which is then manipulated using some arrangement of filters, amplifiers and modulators. A basic understanding of what an oscillator, filter, LFO and envelope is, and how each element affects the others, should be enough to broadly shape sounds with most hardware or software synths. Aside from the most straightforward analogue synths though, most instruments will offer some variation on these basic elements, which is usually where the distinctive character of each synth lies.
Ways and means
Analogue-style oscillators, for example, generally offer the same set of waveshapes as standard – saw, square, triangle and sine – but often include features that allow these to be morphed into more unconventional shapes.
The most common example of such is pulse-width modulation (PWM) applied to a square wave oscillator. The cycle of a square wave has an equal balance of maximum (on) and minimum (off) voltage. Adjusting the pulse width changes this balance between the on and off elements, which has a significant effect on the harmonic qualities of the sound produced. Pulse-width modulation allows this to be controlled, often by an LFO, resulting in a shifting timbral quality with a phasing-like effect, reminiscent of bowed string instruments.
Other oscillator effects might include cross modulation, which allow for one oscillator to modulate characteristics such as the frequency, phase or amplitude of another. The key difference between this and more conventional modulation from an LFO is that an oscillator will operate at audible frequencies, meaning it will alter the harmonic content of the destination oscillator.
In the case of a subtractive synth – ie, most analogue-style designs – most elements of the engine are there to remove portions of the raw oscillator sound. Filters remove frequency content past a defined cutoff point, while the amp raises and lowers the amplitude of the sound to create a volume contour. Features like PWM and audio-rate modulation are important as they allow the user to add complexity to the raw sound of an oscillator – adding to tonal character in a way that isn’t possible using these other subtractive elements.
Find what works
When experimenting with these tools, you’ll quickly discover that some are more harmonically pleasing than
