In this video, we're going to delve into frequency modulation synthesis.
It is a beautiful type of synthesis, but I
will admit it's quite hard to get your head around.
When I first started exploring FM synthesis,
I really couldn't figure out why I was getting the results I was getting.
In fact, I still have a hard time imagining a sound
and then creating it with FM synthesis.
More often, I'm playing around with the synthesizer.
And when I stumble across something I like, I save it
and I move forward from there.
And I would encourage you to work that way as you dig into FM synthesis,
and with all synthesizers, really.
But let's see how FM synthesis really works.
The benefit of FM synthesis is that it's very low CP usage
and you're creating complex timbres simply with sine waves.
But the way we're using these sine waves is a little different.
In all the synthesizers we've looked at so far,
there really were two types of signals.
There was the alternating audio signals that we were hearing,
but there also were these modulation signals,
the things that I've been setting up with the Max for Live devices
by saying map with a source and a target.
We can call that a control signal.
And we're quite familiar with modulating frequency with an LFO.
Let's try it out here.
I have a simple experiment set up.
I have a sine wave generator.
Currently it's at 320 Hertz.
I have an LFO, which I've mapped to control the pitch of the sine wave
generator.
And I have a spectrum device here so we can see the results.
Let's hear the sine wave.
[SINE WAVE]
And then I'm going to modulate its frequency.
[SINE WAVE VIBRATO]
And this type of modulation, the modulation of frequency using an LFO we
call vibrato.
It's a very common type of modulation.
It's a cyclic variation in pitch.
But what happens when we start speeding up that modulation until it's
really, really fast?
[SINE WAVE QUIVERING]
Throughout this course, I've been intrigued by these perceptual barriers
and these barriers of ranges.
Certain things happen at the sample level that impact the signal level,
and certain things happen at the signal level
that impact this perceptual level.
And some of it's hard to understand those transitions.
And this is one of those things where if we modulate frequency fast enough,
we start to see new frequencies emerge.
We start to see these sidebands.
And I'll go slowly through this.
You'll hear vibrato.
And then after a while, you stopped hearing vibrato.
It just sounds kind of rough.
And then as I keep going, you start noticing
these other frequencies that are actually
symmetrically around that center frequency.
Let's go through this again and try it.
[SINE WAVE QUIVERING]
Right now, I'm hearing a vibrato.
I hear that sine wave move left and right, move up and down.
I'm going to increase the depth a little bit so it's moving over a wider range.
Now, I'll start speeding that up.
[SINE WAVE QUIVERING]
We still hear it as this really fast wobble frequencies.
Suddenly, it starts to become rough.
And in the spectrum analyzer, I can start to see these peaks form
right around that center frequency.
As they go further and further as I change the rate of that modulation,
I can see and hear those peaks spread out from that center frequency.
We call those peaks sidebands.
By carefully controlling the location of the sidebands
and the frequency and depth of the modulation,
we can create a wide variety of timbres What it really is is just really,
really sped up vibrato.
And that is the foundation of FM synthesis.