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Making Digital Synths Sound Warm Is Easier Than You Think

by DJ Pangburn, iZotope Contributor August 1, 2019

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Analog or digital—which side are you on?

Or at least that’s how the decades-long debate has played out in the minds of synthesists, both novice and professional alike. But the synthesized sounds that producers and musicians use really shouldn’t be an either-or proposition. Unless one is aiming for a particular sound, like the vintage modular of early Wendy Carlos records (see: The Well-Tempered Synthesizer), why not use whatever is at your disposal? 

While it is true that digital synth can’t truly replicate the variable, slightly unstable electric currents of vintage analog gear (how could it?), it’s a mistake to assume that digital can’t sound warm. Over the years, digital synths, whether they be FM synths, wavetable, or some other type of DSP technology, have become incredibly powerful and flexible—it just takes tweaking to bring out the warmth. 

A small bag of tricks can bring analog warmth to a digital synthesizer—things like filtering, EQing, LFOs, and so on. The same goes for virtual effects plug-ins. Before we dive in, take the time to familiarize yourself with some basic synthesis concepts:

Simple FM Synthesis: Sine Waves and Processors

The Basics of Granular Synthesis

Soft Synth Essentials: Oscillators, Envelopes, and Filters

The Beginner’s Guide to Synthesizers for Music Production

LFOs on Synths and Beats

Digital Audio Basics: Sample Rate and Bit Depth (for those wanting to dive into audio fundamentals)

Now, let’s get into some techniques for making digital synths sound warm. No, we’re not trying to sound "analog" exactly. We’re just talking about techniques to achieve a certain desirable warm tonality that goes beyond analog versus digital, and can work whether you’re using a hardware, software, or sample-based synthesizer.

Teenage Engineering OP-Z multimedia synthesizer and sequencer

For our audio clips below, we used the OP-Z, a new multimedia digital synthesizer and sequencer from Teenage Engineering. A powerful and flexible digital synth, it is capable of a variety of sounds. The factory presets sound pretty digital, but with some onboard tweaking of parameters, alongside some optional DAW-based effects, it can get quite wide and warm indeed. 

Detune your synth note or chord to add warmth 

A good way to infuse a synth note or chord with warmth is to detune it. In analog subtractive synthesis, two or more oscillators are often set to slightly or vastly different pitches. This adds thickness and depth to the sound that moves a digital synth away from a cold or clinical digital signal.

Oscillators can be detuned on many software synthesizers, but also on modern digital synths like the Novation PeakAccess VirusWaldorf BlofeldRoland Boutique D-05, and others. On the Blofeld, for instance, each of its three oscillators can be tuned differently. Another way to do this is to record each voice separately and detune or transpose once the audio is in a DAW.

Transposing OP-Z down 1 semitone (detuned 100 cents)

Another detuning technique is to assign one or more LFOs to modulate oscillator pitch; ideally at slow rates to give the synth a more organic sound. Yet another way of creating a detuned sound on a digital synth is by recording one track at one pitch, then recording it again at another pitch. By stacking or layering these differently pitched synth notes, that detuned warmth will surface.

For our first clip, the synth is at its factory pitch. In the second clip, we detuned the synth one semitone in Ableton Live, as detuning isn’t possible on the OP-Z. It’s a small step, but we’re on our way.

OP - Z - Factory Pitch

OP - Z - Detuned

Noise and distortion are your friends to add subtle warmth

Detuning oscillators may not be the answer for every situation that requires depth and color from a digital synthesizer. Adding various types of distortion and noise is typically a good option, even for relatively clean tones.

As we’ve discussed, white noise is a flat “shhhh” sound created when all frequencies are have the same amplitude.  It sounds like high end noise to the human ears, but when used judiciously in combination with other synth parameter tweaking and effects, white noise can help add some color to a synth's harmonics.

Trash 2's "Grainy" Tape Saturation preset applied to the OP-Z

Similarly, adding a bit of drive to a synth, with either an onboard distortion option or a plug-in like Trash 2, will enhance these warmer, grittier harmonics. And if that isn’t enough, some tape saturation, which can also be found in Trash 2, is a great option. Bit reduction—lowering the bit depth from 16 or 32 bits to something like 8 bits—can also add a bit of noise to a signal, removing some of that pristine digital clarity.

Try various combinations of these four effects. A little white noise with drive, or perhaps some bit reduction with tape saturation. And if you really want to experiment with your sound design, try all four. These four are all very powerful effects, so moderation will be key when finding that sweet spot of warmth.

In the following clip, we added some drive on the OP-Z. We then followed that up with some tape saturation on Trash 2 with the “Grainy” preset.

OP - Z - Drive + Tape Sat

Filter & EQ your frequencies for added warmth

For analog and digital synths alike, one of the most helpful tools in your arsenal is the filter section. If a digital synth patch sounds too cold, tinny, or otherwise too artificial (not that artificial is a bad thing), adjusting the filter cutoff and resonance becomes absolutely vital.

First, trim the higher frequencies using the filter cutoff. This allows you to get right to those low and low-mid frequencies that supply desirable warmth. Pushing the filter resonance adds color to the signal as well. Too much resonance, however, can produce a ringing feedback frequency, which will counteract the goal we have of making the synth sound warmer.

OP-Z app, showing adjusted envelope (P1), filter cutoff frequency (FILTER), and resonance (RES)

If the filtering isn’t getting the desired warmth, it might be time to turn to a few bell filters in your EQ. This will allow you to adjust multiple frequencies, instead of just cutting out entire frequencies with low- and high-pass filters.

Ableton Live and other DAWs typically come equipped with some EQ options. But, if you require more flexible control over equalization, other EQs like the one in Ozone have additional features. Access to dynamic EQ and the option to have multiple EQs in a single plug-in lets you adjust frequencies in ways that stock EQs usually can't. This flexibility gives you even more ways to dial warmth and color in.

We cut out some of the OP-Z's high and mid-frequencies, closing the oscillator envelop a bit as well. Since I'm happy with the filtering, I choose not to fine-tune the remaining frequencies.

OP - Z - Filter + Env

Effects considerations for adding warmth to digital synths

All of the above will, in some combination, create a great deal of the warmth that you’re after. But if it still isn't enough, try adding some effects to further enhance your sound.

Adding a chorus effect will add depth to the warmth you’ve created. Again, too much chorus will defeat your efforts, so moderation is key. If chorus doesn’t trip your trigger, reverb will help add some nice overall atmosphere to the warmth. But, as with noise and distortion, use reverb judiciously. A very short delay, like tape echo, will also add to that depth and warmth.

iZotope DDLY plug-in

For our purposes, we added delay, chorus, and reverb on the OP-Z. We also added a little tape echo using DDLY. Listen to the final results in the audio clip below.

OP - Z - Chorus + Delay + Reverb


Ultimately, there are no big rules for creating warmth, only tactics. Experiment. Get creative and see what works for you. Let thy ears be thy guide.

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