Transcript Basic Tools for Understanding Synthesis Synthesizer  A musical instrument that produces waveforms, typically in the audio range of about 20 to 20,000 Hertz, electronically.  Types of.

Basic Tools for
Understanding Synthesis
Synthesizer

A musical instrument that produces
waveforms, typically in the audio range of
about 20 to 20,000 Hertz, electronically.

Types of synthesis include Subtractive
Synthesis, additive synthesis, wavetable
synthesis, and physical modeling.
In Simplest Terms
1.
The oscillator creates a waveform - VCO
2.
The filter rounds down the wave to the requested
amount of brilliance. -VCF
3.
The wave is amplified by the amplifier to the
requested sound level- VCA
4.
Modify your sound by attaching another oscillator to
your sound at any point listed above. LFO
Bogus Abstraction:
Energy
VCO
•Electricity (Energy) is required to get an oscillator to
produce a sound (Wheat).
•The Sound (Wheat) is filtered by VCF (bowl) and then
sent to be amplified (cooked)
•We can shape what we filter with an envelope
•We can shape how we amplify with an envelope
•We can add more color by adding another wave to one
of the modules. (Add Spice with LFO)
VCA
VCF
Envelope
Envelope
LFO
Synthesizer technology is broken up
into two categories:
"analog" and "digital".
Let’s Start with Analog
A typical analog synthesizer consists of:
• Keyboard,
• 2 oscillators,
(at least)
• A low frequency oscillator (LFO),
• 2 envelope generators
• A filter
• Voltage control amplifier (VCA).
Creating Sound

When a key is depressed on the keyboard a
pitch control signal is sent to the oscillators
(VCO- Voltage Control Oscillator).
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An oscillator is a circuit that creates a single
periodic wave form at a desired frequency
VCO-Voltage Controlled Oscillator
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An electric device that creates a frequency by
a voltage input.
Altering the voltage- alters the produced pitch
Provides simple source waveforms
simultaneously
Oscillator produces saw tooth and then other
waveforms derived
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Rectify saw -> triangle
Hard clip saw -> square
Soft clip triangle ->sine
First Pathway
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The oscillator generates the desired
frequency and wave form and then routes an
audio signal to the Voltage Control
Filter (VCF)
Waveforms that can be created:
Second Pathway
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The keyboard has also sent control signals to
another part of the synthesizer, the envelope
generators.
There are usually 2 envelope generators in a
synthesizer. One controls the Voltage Control
Filter (VCF) and the other the Voltage Control
Amplifier (VCA)
Two pathways
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The first control signal that is sent to the envelope
generators is called a "trigger"
Trigger and Gate
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The "trigger" sends a message to the generators
telling them a key has been pressed. This begins the
envelope generator's process of creating an envelope
for the wave form being generated by the oscillators.

As long as the key on the keyboard is
held down, another control signal, the "gate" is sent
to the envelope generators. The "gate" signal tells the
generators that the note is still being played and the
envelope being generated will stay open until this
"gate" signal ceases
What is an Envelope?
Attack, Decay, Sustain and Release
The envelope is a control signal that can be applied to various
aspects of a synth sound, such as pitch, filter cutoff frequency, and overall
amplitude.
Envelope generators are used to help the synthesizer shape the sounds. They allow you to alter
sounds by sending a varying control signal to the synth's VCA and VCF.
Routing
The output of one oscillator/generator is
hardwired to the Control Voltage (CV) input
of the VCF, and the output of the VCF is
wired to the CV input of the VCA.
Filtering
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A device for eliminating selected frequencies from the sound
spectrum of a signal and perhaps (in the case of a resonant
filter) increasing the level of other frequencies.
Traditional analogue filter types
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high-pass
low-pass
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band-pass (series combination of low and high pass)
Notch (series combination of low and high pass)
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Or a combination (e.g. voice formants look like multiple band pass
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Also known as “Modulation”
The process of sending a programmed signal
to a sound source so as to change the
character of that sound.
VCF-Voltage Controlled Filter
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Cutoff frequency (and perhaps Q) controlled
by amount of input voltage
Typical filter has fixed -6dB/oct slope and
constant Q
Voltage-controlled slope useful for emulative
synth – but hard to implement
VCA – Voltage Controlled Amplifier
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A device that responds to a change in voltage
at its control input by altering the gain of a
signal being passed through it.
Provides control over signal amplitude
Gain controlled by voltage input
Several inputs provide simple mixing
Modulate your modules!

The use of the LFO (Low Frequency Oscillator), also called the sweep or
modulation generator, will shape or texture a property of another
waveform.

The LFO produces sine and triangle waves in the sub-audio range, usually
below 9 Hz, that contour the shape of the waveform they are sitting
underneath. The LFO can be routed to modulate almost any module of the
synth
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An LFO routed to the VCO creates a change in pitch (vibrato).
A LFO routed through the VCF will alter the tone color of the sound (trill).
Modulating the VCA will change the amplitude (tremolo)
Other types of modulation modules that aren't available in every
synthesizer are: the ring modulator, which acts on the principle of
amplitude modulation, and the random note generator.
Ring Modulator

A type of mixer that takes two signals and
produces either the sum or difference of the
two signals. Used in the 70s but not heard of
much in the modern era.
Frequency Modulation

A change in the frequency (pitch) of a signal.
At low modulation rates, FM is perceived as
vibrato or some type of trill, depending on the
shape of the modulating waveform. When the
modulating wave is in the audio range (above
20Hz or so), FM is perceived as a change in
tone color.
Mod Wheel

A controller, normally mounted at the left end
of the keyboard and played with the left hand,
that is used for modulation. It is typically set
up to add vibrato.
After Touch

A type of control data generated by pressing
down on one or more keys on a synthesizer
keyboard after they have reached and are
resting on the keys.
A BIT OF HISTORY :

In the mid 60's, Robert A. Moog discovered that the gain of an amplifier
could be controlled by a DC voltage: the VCA was born. Taking into
account the design similarities between an Amplifier, Oscillator and
Filter , there was no reason to believe that a VCO and a VCF couldn't' be
constructed as well. This major discovery was going to revolutionize
electronic music production for the years to come, for it was now possible
to construct a musical synthesizer entirely Voltage Controlled by DC
voltages.
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Around the same time, American composer and pianist Walter ("Wendy ")
Carlos , was looking for a new technology to enhance his musical
performances. Eventually, W. Carlos met Bob Moog, and asked him to
develop an electronic instrument, using standard keyboard keys, which
could synthesize new sounds: The MOOG Music System 55 was born.
Modular Synthesizer
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A form of Synthesizer that is comprised of a number
of primarily independent units. Each unit, or Module,
performs a limited number of functions.
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Modules may be broadly categorized as audio
generators:
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Oscillators
Control voltage generators (such as Envelope Generators),
Signal processors (including Mixers, Filters, and VCA).
Patch Cords are needed to connect modules together.
Normalled Synthesizer
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Examples of 'Normalled' Synthesizers would
include:
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Minimoog
APR-2600
This type of synthesizer has modules already
connected together in a useful way, however, these
connections can be over-ridden by inserting a cable.
It's somewhat like having presets which can be used
or ignored.