We're going to delve into more depth in synthesis and signal processing.
How do the audio effects that we looked at in module two actually work?
And how do the the virtual instruments that we
we're using in module three actually work?
How does all this stuff come together to actually make sound and transform sound?
I want to talk about the basics of synthesis and signal processing.
What they are, what the difference between them is.
And some of the reasons we might want to implement our own synthesis or
signal processing systems, and some of the challenges we might encounter in doing so.
So synthesis is essentially generating audio from scratch.
So not going with a microphone and
recording it and then editing or doing something with it.
But generating it, from scratch by either analog or digital means.
So you can imagine we have this wave form here
like the ones we have been looking at through the, the whole course.
And you can imagine that we are generating this entire wave form
from scratch on the computer.
So how would we actually do that?
It's it actually goes back to what we were talking about in the very first lecture in
the course, this notion of a waveform is a function, like y equals sin x or
something like that.
You can imagine that we can synthesize a sine wave since no
perfect sine wave is ever going to exist till we can capture it on microphone.
We'd have to synthesize this from scratch.
And so we can simply use this function,
sin(x) to figure out what the amplitude value should be at every sample over time.
So this is a fairly straight forward example of synthesis in
making a sine wave.
It turns out there are a lot of different techniques that we can use to synthesize
sound beyond just assigning simple functions like this that can give us
more flexibility and power to shape what that sound is actually going to be like,
what it's timbre is going to be.
We're going to look at four types of synthesis there are many more, but
these are four very important ones.
Additive synthesis creating sounds by adding together a bunch of sine waves or
other basic wave forms.
Subtractive synthesis, which is kind of the opposite starting off with
a very rich sound source like a white noise, for
instance and then filtering it and kind of sculpting it.
Modulation synthesis, which is using an oscillator like a sine oscillator or
something like that to actually create an envelope that controls some other
parameter for sounds and granular synthesis, which is about looking at
a sound not so much in terms of wave forms but as these tiny grains,
these tiny little bits a few milliseconds each And and creating tens of thousands of
these every second to create this notion of a kind of cloud of sound or texture.
So that's what synthesis is and some basic types of synthesis.
So what is the difference between synthesis and signal processing then?
Signal processing is about transforming existing audio the same way
we've done when we've added audio effect to tracks and reverb.
The same way that effects pedals work when we plug a guitar into an effects pedal.
We get in some kind of a source audio and
we do something to it and send the transformed version out.
When we do this in the,
the digital domain, we tend to call it DSP, that's digital signal processing.
And a lot of the same techniques that we looked at on the last slide here,
additive, subtractive, modulation and
granular these mostly can be applied to signal processing as well.
So they can create sounds from scratch, but
we can also adapt these these techniques to process existing sound.
So why would we actually want to to
synthesize in particular our own sounds from scratch?
Why not just use kind of what's out there already or why not just you know,
get musicians to play violins and pianos and guitars and
all that, to just come into the recording studio and record them with a microphone?
There's a bunch of different reasons we might want to do this.
I want to highlight two and give you some historical examples of why
this has been important to composers over the years.
The first reason is a question of control and precision really goes along with this.
This notion that human beings can't play perfectly quantized rhythms like
the ones that we we created when we, when we edited MIDI data in module three.
Or a composer might want to create incredibly complex rhythms like the the,
the tempo relationships that did with his player piano rules and
his player piano studies.
But there are things that are incredibly difficult or
impossible for human musicians to actually realize with complete precision.
computers, on the other hand, are very good at
doing exactly what they're told and, and realizing things very precisely.
And so if we, if we work with synthesized sounds that we can control via
MIDI Sequencer or via computer algorithms, so that we might write ourselves
it gives us a, a degree of control over every aspect of the music that,
that we might not have if we were simply writing a musical score and
then handing that off to other musicians to perform on conventional instruments.
One example of this that I really like is a piece by
Milton Babbitt called Ensembles for Synthesizer from the mid 60s.
And this was a piece written
at the Columbia Princeton Electronic Music Center.
This one of the first centers for
the study of electronic music based in a university in the United States.
And when it was when it was founded, they purchased this
this incredible synthesizer called the the RCA Mark II.
And this one of those things that took up an entire room.
It was not a digital synthesizer, it was an analog synthesizer, but you can
control it with this this kind of paper tape that went through it that controlled
all these different parameters about the sound you were making very precisely.
Not just the rhythms and the pitches but
also very precise aspects of the timbres and how those timbres were created.
And Milton Babbitt perhaps more than anyone else really fell in love with with
this synthesizer because he, he was using the, the, these complex approaches to,
to organize and structure every aspect of his music.
And he often wrote for, for human musicians on, on conventional instruments,
but he found that RCA let him achieve this level of precision and
kind of realize these structures in ways that might not be possible if
he was working with traditional instruments.
So Ensembles for
Synthesizer is a great example of the work he did with the RCA Mark II.
The other reason, that I want to point out, that people might want to
synthesize their own sounds from scratch is that they want to create completely new
timbres new sounds that don't exist in the physical world in any way.
And a classical example of that is a, a composer who's his name is
Edgar Varese who's considered by many to be kind of the,
one of the founders of, of electric music even though he, he didn't have access to
technologies to make electronic music for most of his life.
It was only at
the very end that he was able to create some works with electronics.
But throughout his entire career as a composer, he was exploring ways to make
new sounds in performance and to think about sounds differently.
And this piece that he finished in
1931 called Ionisation is a great example of that.
It's a, it's a piece that's only for percussion.
So there, there are no real traditional instruments in,
in the ensemble he composed for.
And even within these percussionist that he, he wrote this music for and there's
some traditional percussion instruments like a snare drums and things like that.
But there's also some instruments that,
that you might not of thought of as instruments.
Like a, a siren, for instance.
And what he was really trying to do was to, to create new kinds of timbres and
sounds that you you didn't normally think of hearing in a concert hall you know,
when say, an orchestra played.
So you can expand the pallet of timbres that we thought of as being musical.
It's particularly think about how to organize those timbres musically of his,
his notion of organized sound is still an idea that's important in
electric music composition today.
So I think Ionisation is this great early example, this kind of
pre-electronic example, this search for new sounds that ultimately led musicians
to turn to synthesizing sounds in order to create these radically new things.
Now I want to follow
up that idea about the search for sounds and timbres with a caution.
And this comes from one of the pioneers of
computer music who developed some of the very first languages for computer music.
And I think this quote really sums it up really beautifully.
Max Matthews, it is very hard to create timbres we hear as interesting and
powerful and beautiful.
What he's really trying to say here is, anyone can sit down and
create a synthesis algorithm and create a synthesizer, but the overwhelming majority
of these new sounds that you create with a synthesizer are going to sound horrible.
They're not going to sound musical, and no one is really going to want to use them.
What's the real challenge here is, is, is, is not making something new,
but making somethings that's, that's worth making that's new.
And that's, that's really where the challenge of synthesis and
sound design comes in.
They may feel very simple and limited as we look at them,
but as we see how they can be extended in, in, different ways, we'll see how they be,
they can really become rich ways of synthesizing sound that that,
that had the potential to, to meet this challenge.
So what we've looked at in this unit is is what synthesis is and
what signal processing is and and some of the, the issues and,
and motivations behind using them.
I want to look at a very fundamental idea that's required to do that, and
that's the notion of unit generator.