Join Alex U. Case for an in-depth discussion in this video Get in the Mix: Modulation rate and depth, part of Audio Foundations: Delay and Modulation.
Delay effects based on a changing delay introduce a whole new layer of interest to your mix. A changing delay is an ear-grabbing alternative to the fix delay, and it has an intriguing side effect. Changing the delay, also changes the pitch. The slow modulation of delay time that is common in so many effects, introduces a slight detuning of the track. A moving delay leads to a wobbling pitch. We have to be careful here, because an out of tune track can sour any production. But if the delay modulation is slow, the pitch bending might be a subtle positive.
It can sound human and expressive. On the other hand, if you want an aggressively altered pitch pattern as part of a special effect, don't hold back, and let a modulating delay do the job. So let's listen to what the modulation section can do. We'll start here with the modulation rate and depth, and cover modulation shape in the next video. Rate controls how quickly the delay time parameter within the effects device is changed. You'll find mixed situations when you want to sweep the delay time imperceptibly slowly, and other times where you need a fast, very audible ray.
This electric guitar provides a good illustration. The electric guitar, abbreviated EGT, feeds a bust to the aux input labeled echo, which in turn has a medium delay plugin inserted. Adding a fixed medium delay with the duration around 30 to 40 milliseconds creates a kind of doubling effect. An effect we explore in more detail later in this course. Hear how it almost sounds like two guitars? Modulating this delay transforms and upgrades this effect substantially. I'll raise the depth now so that the modulating LFO has some amplitude, so that our delay is ready to change when we turn on the modulation section next, which we do by raising the rate control to just a fraction of a hertz.
Now its starting to sound interesting, like two guitars. It seems our ears, our minds really, are quite intrigued by even a slightly changing delay time. To understand this better, let's do something a little unconventional. While this isn't a typical approach during a mix, I'll temporarily convert the aux-send we're using for this delay into a a prefader send. This means the electric guitar signal that's fed to the delay plugin is actually sourced from a point in the daw before the electric guitar fader and mute functions.
We usually don't use a pre-fader send on effects, because we want the effect to rise and fall proportionally, as we raise and lower the electric guitar track in the mix as needed creatively. Push the level up a bit for excitement one moment, and pull it down so it doesn't drown out the vocal the next. So, a post-fader send to an echo effect is typical. But we use a pre-fader send here, so that we can mute the guitar track and still hear the echo. It's a good way to start to hear what's going on. So listen to the output of our slowly modulating delay alone, and I'll increase and decrease the rate control while we listen.
When the rate control is high enough, we hear a strong pitch wobble. That's the sound of a changing delay causing a change in pitch. As the delay time sweeps up to a slightly higher value, the pitch drops down. When the delay time sweeps back down to a lower value, the pitch swings back up. Pitch change is an inevitable side-effect of delay modulation. Even at this very slow modulation rate, the guitar is slightly detuned. If you aren't noticing the pitch wobble here don't worry, it's subtle and slight, but its absolutely there and its an essential part of effects like doubling, chorus, spreaders, and thickeners discussed elsewhere in this course.
We may not hear a pitch change directly, but our ears and brains do grab on to something different. Lets add the original electrical guitar back into the mix and listen to what happens as even this very slowly modulating delay is pulled down to a rate of zero hertz. No modulation. Hear how the effect becomes much more disappointing when its a static medium delay? As soon as the delay time is changing, even slightly, so slowly that we don't actually hear a pitch change when listening to the delay alone, the effect becomes indescribably more interesting.
When two guitarists play the same part, they're never perfectly synchronized. We know that note for note, one guitar will play a fraction of a second ahead of the other, and I'm not picking on guitarists here, any two musicians will exhibit at least slight performance timing variations. This medium delay effect is a starting point for simulating two guitarists from one, but a modulating delay adds more realism to this effect. With two different performances that time offset between them doesn't remain perfectly fixed.
It flexes and moves humanly, a bit early one moment and a hair later the next. The modulating delay is therefore far more convincing than a fixed delay at creating a doubling or chorus effect. And file this observation away, fixed delays lead to great effects, but changing delays, even slowly changing delays, lead to surprising, textually strong results. You'll owe it to yourself to explore this. Depth controls how much the delay is modulated. It bounds the delay time at the extreme to finding the shortest and the longest delay times allowed.
The original fixed delay time might be increased and decreased by five milliseconds, ten milliseconds, fifteen milliseconds, or more. Listen to the delay output with rates set to a couple of hertz, and depth cranked to its highest extreme. I'll then reduce the depth to a more modest level. Listen carefully to how the extreme pitch wobble is narrowed. At high depth settings, I'm getting a bit motion sick. The guitar's on a boat? Reducing the depth control doesn't stop pitch shifting from happening, but it tames it significantly.
Depth controls the total range of delay modulation, and rate controls how fast it gets there.
- Adjusting the delay time, level, and feedback parameters
- Utilizing a low-pass filter and polarity reverse
- Setting up an effects loop
- Setting the delay time by tempo or by ear
- Understanding the distinct uses of short, medium, and long delays
- Adjusting modulation rate, depth, and shape
- Adding double tracking and spreader effects
- Manipulating tone with constructive or destructive interference
- Creating a comb filter and flange effect
Skill Level Intermediate
Q: This course was updated on 01/31/2014. What changed?
A: The Get in the Mix videos have been updated to the most recent version of Pro Tools. Also, the course now includes free Get in the Mix sessions for two more DAWs: Logic Pro X and Pro Tool.