The Third Leg Of The Stool: Timbre
We’re in the home stretch! This is the fifth post in a series of six posts. If you’re looking for a comprehensive overview of mixing, you may want to read the earlier posts first: Mixing Is A Three Legged Stool, The Seat Of The Stool: How To Listen To Music Like A Mix Engineer, The First Leg Of The Stool: Volume, and The Second Leg Of The Stool: Space. Or maybe you don’t want to. I don’t know. I’m not your boss, so you do you.
Once you’ve dialed in the volume of your tracks and established the space for your song, you may find that some of your sounds no longer feel as present or vibrant as they did when you were recording them. That’s normal! Sounds in a song exist in a context. If you’ve already considered whether you should go back and re-arrange some parts of your song and you’re sure you shouldn’t, then considering timbre is the next step on your journey. Once your volume and space are right, timbre is the last lever for presence.
As a reminder, timbre is the character of a sound: its harmonics, its texture and grit, its density. For the purposes of this post, I’m going to steer clear of timbre adjustments so severe that they amount to sound design (and therefore composition or production) choices and stay focused on how to make subtle shifts to timbre that help sounds feel more prominent or more vibrant in a mix while still maintaining their core sonic signatures.
When working to adjust timbre for mixing, you have two primary schools of effect to utilize: modulation and saturation.
Modulation Effects In Mixing
What Are Modulation Effects?
What are modulation effects? They’re audio effects that use cyclical changes over time to manipulate the source signal. Often that means they use low frequency oscillators (LFOs) and delays (especially bucket brigade style, or BBD delays) to affect volume, pitch, or phase. The most common modulation effect is probably chorus. Other common modulation effects are phaser, flanger, and tremolo. Chorus, phaser, and flanger are all modulated delay effects. Tremolo is a modulated volume effect.
Chorus functions by duplicating a sound, slightly delaying and pitch-modulating the duplicate, and playing it back in parallel to the dry signal. The delay time of most choruses is pretty short, typically under 50 ms. Chorus creates a shimmery, wobbling effect.
Flanger works by creating a duplicate of your dry signal and delaying one of those by a constantly changing amount, which is controlled by an LFO. This creates periodic phase cancellation and interference, resulting in a sweeping, swooshing sound.
Phaser operates by duplicating the audio signal and running one of the signals through a short delay and an all-pass filter, which flips the phase of some of the frequencies. The all-pass filter is typically modulated by an LFO that continuously shifts the frequencies that get delayed. Phasers create a spacey, swirling sound.
Tremolo uses an LFO to control the volume of a signal, raising and lowering the volume periodically to create a pulsing sound.
Each of these effects can be used in subtle or extreme ways. If you’re using these in mixing and not trying to fundamentally change the sounds in your music, restraint is key. My advice is to either use effects that have a wet/dry setting or set them up on a send bus so you have very fine control over their levels. Finally, you should probably only use one of these on any given sound. And if you find yourself needing to use modulation on several tracks in your mix, I’d encourage you to seriously consider the sound design, production, arrangement, and the mix so far. Needing to rely heavily on these is probably an indication of a weak link earlier in the process.
How To Use Modulation Effects
The first step is likely to set up a send effect with your effect on it. If you’re using a send, make sure the effect is set to 100% wet. Send your instrument to the effect (post-fader), and listen to the effect send to dial in the sound you like, then solo your instrument and the effect, and drag the volume fader all the way down on the effect. Bring it up slowly and find the point at which you can just barely hear the effect blending with the dry sound. Now, turn off soloing and listen to your sound in the context of the mix. You may need to raise the level of the send effect ever so slightly to make sure it’s cutting through the rest of the mix. Mute and unmute the send effect and make sure it’s not too loud and not altering the sound.
What you’re looking for is a little extra sparkle. Typically, chorus is my go-to for this effect, especially for mid-range heavy sounds. I often find flanger works well for low-mid and bass sounds, and that phaser works well on higher-pitched sounds. This isn’t a rule, and maybe not even a guardrail. But it’s a good starting point, and you can make adjustments, try out other effects, and so on as you go.
Using modulation as a mixing technique is especially effective when you want to add energy to make a sound more apparent without changing its mix level. So, for instance, perhaps you have a sound that’s present in the verse and the chorus of a song, and you want the sound to pop a little more in the chorus of the song without dominating the volume. Turning on your send effect for an isolated section of your song can help the sound to pop through. You can also use width-enhancing tools on your send effect to make just the effect occupy a different space than the original signal, thereby creating an interesting and attention-grabbing psychoacoustic effect.
Saturation Effects In Mixing
What Is Saturation?
Saturation is, basically, distortion. But it’s important to remember that not all distortion is guitar pedal distortion. Fundamentally, saturation is just controlled harmonic distortion, typically caused by overloading analog components or by using digital emulations that simulate the behavior of analog overload. Saturation adds harmonics to a sound, which makes sounds feel bigger and richer without necessarily making them louder. When used sparingly, saturation warms up a sound and makes it feel more present in a mix without audibly changing its tonal character.
When you add harmonics, you’re adding density to the sound by adding layered frequencies that are integer multiples of the original sound. Let’s say you have a pure 440 Hz tone; an A4. The second order harmonic of that tone is 880 Hz, the third order is 1320 Hz, and so on. If you use a saturator that adds harmonic overtones, you are adding sound at multiples of 440 Hz. So, saturation always stays in tune with the original sound and thickens the sound.
There are many saturation plugins, but in my opinion, the only two you need are Soundtoys Decapitator and Black Box Analog Design HG-2. Both can take you into wild distortion territory (and Decapitator will do it very quickly if you aren’t careful), but both can be used with nuance to add a little harmonic distortion to a sound that brings it forward in a mix. I’ll also note that there are some excellent tape saturation tools like the Empirical Labs EL7x Fatso and the Softube Tape that can bring some very nice, vibey saturation to your sounds, but they also often introduce noise, and should be used carefully and sparingly as their effects can get out of hand quickly.
How To Use Saturation Effects In Mixing
Unlike modulation, I prefer to add saturation as an insert. Where you place it in your effects chain matters a great deal. Generally speaking, if you’re using Decapitator, HG-2, or another tube saturation style tool, it’s usually best to add it fairly early in your chain. It’s worth experimenting, but often, my chain will be: corrective EQ -> compression -> saturation. Again, not a rule, and you should experiment with placement to get the desired effect on the actual sound you’re using. If you run tube saturation after too many effects, though, its behavior will often be overly driven by those other effects.
On the other hand, if you’re using a tape emulation (like Tape or Fatso listed above), it’s often best to put them at the very end of a chain, as they’re designed to mimic the effect of tape, which, of course, comes at the end of a physical recording chain. Tape saturation, and the noise it can introduce, is prone to getting over-exaggerated if placed too early in the mix chain.
In general, about 1% total harmonic distortion, or THD, is the sweet spot for mixing. When used for mixing, saturation should remain very restrained. You should be able to hear when you turn the effect off, but not perceive meaningful sonic changes when it’s on. Like with modulation effects, using saturation for mixing is most effective when the effect is turned on and off as a means to pull focus on to a part without raising its volume.
When Should You Use Timbral Effects When Mixing?
First and foremost, you should use modulation and saturation as a means to call attention to a sound. By enabling a faint chorus or a bit of saturation on a sound, you can pull the listener’s attention to a part of a song that you want them to hear more clearly. The effect should usually be relatively subtle so that you aren’t inadvertently redesigning a sound. These techniques are especially helpful in denser mixes when competition for frequency bands is high and in mixes where you’re trying to control for headroom to achieve maximum loudness in a mix.
In Conclusion…
By the time you’re considering timbral effects in a mix, your mix should be nearly done. These are really for final polishing and buffing of a mix. But, that being said, using these techniques effectively when mixing can easily separate an amateur sounding mix from a professional sounding one, and can ensure a lively vibrance to sounds that keeps listeners engaged and makes sure that sounds don’t become dull and lifeless.
The next and final post in this series will bring it all together with concrete suggestions on how to mix a song, end to end.
