Modulate pitch to enhance emotion

There are a couple of different ways to use low-frequency oscillators (LFOs) to modulate audio — and today we’re going to talk about the less well-known one!

(First, for the new people: an LFO is an oscillator, moving at low speed — typically fractions of a second to several times per second — that moves between two user-specified extremes with a user-specified periodicity. Think of a sine wave moving lazily back and forth between +1 and -1! That’s the basic idea.)

I think a lot of us are aware, either explicitly or intuitively, of amplitude modulation — this is where a LFO is applied to the amplitude, or loudness, of a signal. For example: tremolo! When you put a tremolo plugin on a track, or hit the tremolo button on a guitar amp, whether you realize it or not, you’re using an LFO to make the loudness of the track move in and out at a certain depth.

But did you know that you can also use LFOs to modulate pitch? You can!

A real-world example is vibrato. Think of a violinist or guitar player wiggling their finger on the fretboard to give a note motion.

What they’re doing, if you think about it, is that they’re stretching the string subtly and then releasing it back to its nominal tension, over and over. Stretching a string increases its pitch! So what the player is doing is essentially using their finger as an LFO to rapidly modulate the pitch of the note they’re sustaining.

And we can hear how much more emotional and interesting that can make a sound. Instead of sustained notes just sitting there lifeless, they come alive in subtle and stirring ways.

Well, great news: you can apply this same emotion-augmenting technique to tracks of audio in songs you’re working on! And you can do so for free, with a free plugin from Baby Audio called Pitch Drift. Grab that here: https://babyaud.io/freebies

Pitch Drift is extremely simple to use. You set the speed of the LFO by dragging up and down in the wave display, and you set the depth of the LFO with the Amount slider. That’s it. But, wow, is it so effective!

The secret is to use small amounts. I tend to use a pretty slow LFO, turn the amount up until I can hear it, and then turn the amount back down a bit. I think this effect works best for me when it’s tickling at the edges of my perception, as opposed to being overt. But see what works best for you! Maybe you want to turn the amount up and get a woozy, disorienting feel. No rules.

This works wonders on a wide variety of sources: synthesizers, keyboard instruments in general, rhythm guitars, bass — it’s always quick and easy to try, and sometimes yields moving results in surprising places.

Something that I love love LOVE to do is to put similar synth pads on either side of the stereo field, panned like <50% 50%>, and put Pitch Drift on each one, with the controls set similarly but differently on each. You get so many dreamy, moody interactions!

Vibrating with excitement — jamie