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Synthesis Techniques For Emulating Vintage Sounds

Sound Design Workshop By Rory Dow
Published August 2020

Synthesis Techniques For Emulating Vintage SoundsPhoto: Hannes Bieger

Any synth can be coaxed into producing vintage-sounding patches...

Despite analogue synthesizers being more readily available than ever, there is still an art to getting those instantly nostalgic sounds; the textures and timbres that take you back in time. In this article we'll take a look at a range of tips that can be applied to almost any synthesizer, hardware or software. I won't be encouraging use of effects or recording techniques. Instead, we'll be focusing purely on the sound design. Grab your synth and let's go back... way back.

What Makes A Vintage Sound?

The million-dollar question. What is it about '60s, '70s and even '80s synthesizers that make them instantly recognisable? What makes something sound 'vintage' at all? The obvious answer is age. Many have pointed towards technological changes such as surface-mounted circuit-boards replacing through-hole designs. That this difference alone makes vintage equipment sound better, or even just different, is a dangerous topic. In theory, modern surface-mounted designs can achieve everything that older through-hole designs can. Instead, it's more likely that, as technology has improved over the years, individual components have become more precise and new circuit designs have 'improved' to reduce errors and imperfections.

In addition to this, one cannot easily measure the effect that time has on electronic circuits. We're all aware that older synth designs can have flawed characteristics such as tuning instabilities or noisy outputs. Some of that is down to the older components and designs, but some of that will also be due to components slowly failing over time. A 40-year old synthesizer will not sound the same as it did when it was factory-fresh.

The important thing to note here is the consequence that age, plus older components and circuit designs, have on the emerging sound. In general, it can be described as unstable, organic, imperfect... perhaps even human. In the same way that a guitar string can never be plucked the same way twice, analogue synthesizers seem to benefit from anything that adds movement or subtle change to repeated notes, and that specifically seems to be less inherent in modern circuit designs. It is with this in mind that a good portion of the tips and techniques that follow aim to emulate the sonic impact of these imperfections through the art of synthesis.

Keep It Simple, Stupid

Firstly, let's go over a few simple rules which will help any vintage sound design session. With modern synths, especially software synthesizers, which are increasingly complex and feature rich, it is tempting to add the proverbial kitchen sink to every sound. Resist that urge. Vintage synthesizers, even the larger, expensive models, were comparatively simple. Stick to basic oscillator shapes: triangle, pulse and sawtooth (even sine waves were a rarity due to the complicated circuitry involved). Start with a single oscillator and only add more when you feel the patch requires it. If you have access to multiple envelopes, practice using only one — using a single envelope for multiple destinations will result in a sonic signature that is instantly recognisable. If you're adding effects, keep them simple too, maybe just some basic delay and reverb.

Another small tip, which can make a big difference and is often overlooked, is to work in mono. Many modern synths use a variety of tricks to create luscious stereo effects, which is all well and good, but your average 30-year-old synth is liable to have just a single mono output. Keep the synth sound mono, and use stereo reverbs or delays to add width.

Oscillators

Let's move on to the anatomy of a typical synthesizer and see what we can do to each element in order to emulate some of that vintage analogue magic.

Figure 1: A triangle oscillator or LFO with waveform reset enabled.Figure 1: A triangle oscillator or LFO with waveform reset enabled.

We'll start by looking at the source of all sound, the oscillator. In order to make an oscillator behave in a vintage synth-like manner, there are a few tricks we can employ. Firstly, make sure to switch off any waveform reset option. Normally this takes the form of a toggle switch whose effect, when enabled, is to cause the oscillator waveform to start from a specific point in its phase cycle whenever a note is triggered (see Figures 1 and 2). In some situations, this can be desirable for making attack transients consistent, but consistency is not our goal and waveform reset was not a common feature on older synthesizers. With the waveform free to oscillate continuously, you will notice slight variances at the start of every note because the starting phase of the oscillator will be different.

Figure 2: A triangle oscillator or LFO with waveform reset disabled.Figure 2: A triangle oscillator or LFO with waveform reset disabled.

The tuning instabilities we spoke about earlier sound like something to which we ought gladly bid farewell, but a small amount of pitch drift can be an effective way to bring some organic life into a sound, so much so that modern synth makers often include a dedicated parameter exactly to emulate this (Sequential rather gloriously named it 'Slop').

Modern synthesizers often include helpful parameters to assist in making vintage sounds, such as disabling waveform reset or increasing oscillator 'slop'.Modern synthesizers often include helpful parameters to assist in making vintage sounds, such as disabling waveform reset or increasing oscillator 'slop'.If you haven't got a dedicated parameter, don't worry, it's easy enough to emulate. A slow LFO, applied to individual oscillators (or the overall pitch of the entire instrument) is a great place to start. Like the oscillator, make sure the LFO isn't resetting with every note. A triangle waveform will work nicely (and give a nice Boards Of Canada effect when pushed, but make sure the LFO is global, not per-note). A slow random LFO (not S&H) is also a good option, which will give a less obvious, more haphazard pitch drift.

Noise Is Your Friend

Almost all synthesizers offer a noise source that can be mixed in with the oscillators to add some grit to a sound. If your synthesizer will allow it, instead of adding noise at the mixer stage, try using it to modulate oscillator pitch. In small amounts, this is an amazing way to 'age' oscillators. You don't really hear the noise, but it has a destabilizing effect. If you increase the amount, the oscillators begin to sound broken in rather a delightful way, achieving that 'failing component' sound we discussed earlier. I first discovered this trick on the Roland SH-101, and it's become a favourite way to inject a vintage feel into any patch.

Using noise as a modulation source can be a great way to destabilize oscillators and filters.Using noise as a modulation source can be a great way to destabilize oscillators and filters.Using noise as a modulation source can work in some other unlikely places too. For example, if your synth has an onboard delay and a modulation matrix that allows it, try modulating the delay time with noise. You'll be rewarded with a lovely smearing of the delay signal which broadens as the feedback increases in a similar way to tape delays.

Filter Tricks

The filter is such a huge part of any sound, and there are ways to help make even the most modern, digital filter to be more like its elders. If you are using a digital filter, try to keep the input levels in the low to medium range. Most filters are designed to saturate and add harmonics when the input level is high. In my experience, many digital filters don't do this convincingly and so it is better to avoid that tell-tale digital distortion if you can. A lower input signal will allow the oscillators to pass though cleanly and you can always add some more convincing analogue overdrive later down the signal chain. Obviously, your mileage will vary depending on the synth. Pushing the input levels higher may be the magic ingredient you're looking for. Experiment and let your ears be the judge.

Much like the oscillator, the filter can benefit from some modulation. The filter frequency is the obvious candidate. Follow the tips we discussed in the oscillator section to add some pitch variation to the filter. Also, if your synth allows it, try modulating the resonance. Again, using noise as a mod source can be astonishingly effective. Vintage synths often have quite unstable resonant peaks. Adding tiny amounts of noise to the resonance whilst adding some triangle or random LFO to the frequency will really help to destabilise the filter.

In reality, there is very little difference between a modern digital synthesizer and an older vintage one, and so it is in these little programming details that we can find that vintage mojo.

You should be spotting a pattern here — the LFO and noise tricks can be used on any number of parameters: envelope times, glide rate, anything that might inject a bit of variation or instability into the patch. Keep it subtle, though. You don't want the sonic impact to be too obvious. Some synthesizers, generally more complex polyphonic software synths, offer different types of random modulation sources. For example, rather than using a simple LFO, there may be a random modulation source which offers different values for each polyphonic note played. Make good use of these if you have them, they add more subtle variation than using a single LFO. This 'micro-complexity' is the addition of many small variations in a patch, all of which you may not be able to hear in isolation, but which if removed as a whole, would make a noticeable difference.

Envelopes

Figure 3: Analogue envelopes will 'restart' from their current level when receiving a new note-on, whereas digital envelopes often restart from zero.Figure 3: Analogue envelopes will 'restart' from their current level when receiving a new note-on, whereas digital envelopes often restart from zero.

Analogue and digital envelopes can have some noteworthy differences. Analogue envelopes will hardly ever reset to zero when a new note is detected. To test this behaviour, try setting up a simple monophonic patch with a long amplitude attack and release. When you first trigger and hold a note, the long attack will slowly fade the sound in and when you release the note, the release time will allow the sound to fade slowly away. If you re-trigger the note during this release phase, the envelope should begin its new attack phase from the current release level, and not from zero. This makes a surprising difference to patches with long release settings. Very few synthesizers will allow you to change this envelope behaviour, and if you're unlucky enough to be working with one which forces a return to zero on every note trigger, then I encourage you to write to the manufacturer and berate them.

Envelope stages sound much more natural with some exponential curve.Envelope stages sound much more natural with some exponential curve.

Envelope curves are also worth consideration. Analogue envelopes are never linear in shape. In fact, it is well known that the ear finds an exponential envelope shape to be more 'natural', and this is the shape most analogue envelopes will use. Many modern synthesizers will offer a curve parameter for the attack, decay or release sections so you can adjust the separate stages. Alternatively, if your synth offers a modulation matrix which includes envelope times as destinations, try applying an envelope to its own decay stage. This will turn a linear decay stage into an exponential decay stage without the need for a dedicated parameter.

Moving On

By now you should have enough small tweaks which you can make to any patch get you closer to a vintage '60s or '70s sound. The tips I've given, in isolation, might seems like they don't make a great difference, but the end result is more than the sum of its parts. In reality, there is very little difference between a modern digital synthesizer and an older vintage one, and so it is in these little programming details that we can find that vintage mojo.

Beyond the synth itself, there are many things we can do to add to the vintage flavour. EQ'ing and filtering to roll off high end, using simple sequencers or chord memory to aid composition, recording to analogue media, even the way you play a synthesizer can all add up to a convincing vintage sound. Just remember to embrace those imperfections — they are the key!

Published August 2020