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 Terms1. 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 VCF VCA

Envelope Envelope

LFO

•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)

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).

An oscillator is a circuit that creates a single periodic wave form at a desired frequency

VCO-Voltage Controlled Oscillator

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 Rectify saw -> triangle Hard clip saw -> square Soft clip triangle ->sine

First Pathway 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 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

The first control signal that is sent to the envelope generators is called a "trigger"

Trigger and Gate 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 ReleaseThe envelope is a control signal that can be applied to variousaspects of a synth sound, such as pitch, filter cutoff frequency, and overallamplitude.

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

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 high-pass low-pass

band-pass (series combination of low and high pass) Notch (series combination of low and high pass) Or a combination (e.g. voice formants look like multiple band pass

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 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 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 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.

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 A form of Synthesizer that is comprised of a number

of primarily independent units. Each unit, or Module, performs a limited number of functions.

Modules may be broadly categorized as audio generators: 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 Examples of 'Normalled' Synthesizers would

include: 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.