breakbeat cafe 

    - Understanding Synthersizers 

  

The Envelope
Controls the ADSR section of a synth as follows:

Attack 
Attack means how long the sound takes to get to full volume
Slow attack makes the sound rise gently in volume (typical for synth pads)
Fast attack makes the sound hits peak volume immediatley (anything percussive) 

Decay 
Affects the time taken for a sound  to drop to the level of the sustain parameter
Fast decay means the sound will quickly reach sustain level 

Sustain 
Sustain is the volume the note will play at as long as the key is pressed down or the MIDI message is on
The constant volume that the sound takes after decay until the note is released 

Sustain specifies a volume level rather than a time period
When a note is released the release parameter kicks in

Release 
Effects how long volume takes to fade to zero after the note has been released 
i.e As soon as you let go of the note, how long it takes to reach silence

Waveforms

Saw-tooth 
Well-suited to subtractive synthesis
Has equal quantities of odd and even harmonics to be creatively removed via filtering
One of the best waveforms for sythesizing musical sounds
Good for bowed string instruments like violin and cello, also work well for synth pads and leads

Sine wave
Sine waves have no harmonics at all which makes for a very pure sound 

Good for bass, good for bleeps, also work well for pure sounding pads

Square waves  
Have only odd harmonics close to the fundamental frequenc.
Square waves sound similar to a sine but with a crisp and ringing quality 

Good for bass and leads 

Triangle waves 
Have only higher odd harmonics
Sound a similar to a sine wave but with a reed like quality

Pulse 
Pulse waveforms look a bit like a square wave but the peak to trough ratio is not equal 

You could call them rectangle waves
They sound like a square wave but with a thinner less natural edge

White/Pink Noise 
This is available on some synthesizers and can be used to make percussion sounds or  wind noises

Filters

Following the process of timbre design by harmonic interference the sound is subsequently routed through filters. This is where the subtractive element of synthesis begins.

Filters are inherent to the process of synthesis in general and are where subtractive synthesis gets its name. This is because filters, filter  out of a sound and can highlight the remaining frequencies which change a sound's character.

Which frequencies are removed depends on: 

1.The type of filter  

2.How its settings are configured

Basic filter settings as follows:

Cutoff 
This is the point in the spectrum at which the filter begins removing frequencies (same as EQ)

Pole number or dB
This is the breadth of frequencies encompassed between the cutoff point and the point in the spectrum where frequencies are reduced to zero in volume. Standards are 6dB, 12dB or 24dB slope per octave. Higher pole filters have less breadth between these points than low or single pole filters.

Resonance or 'Q'
This is the setting that provides specific control around the cutoff frequency, i.e the level of amplitude surrounding the cutoff frequency. Q's are often referred to as being narrow or broad. 

Example:

Set the frequency 2 KHz 

Boost using a narrow 'Q' 

You will only affect frequencies from 1.95 KHz to 2.15 KHz  ish 

With a wide Q you will affect a wider range or  frequencies from 1.3 KHz to 2.7 KHz ish 

The way in which these settings effect a sound depends on the type of filter being used. 

The the most common are:

Low pass filter
Removes frequencies above the cutoff frequency.

High pass filter 
Opposite of low pass, removes frequencies below the cutoff.

Band pass filter 
Flters frequencies at either side of the cut off, creating a muffled or telephone sound. 

Notch filter
Oposite of band pass, removes frequencies directly at the cutoff leaving those above and below. Can be used to reduce unwanted noise..

Comb filter 
A series of high resonance notch filters fixed a small distance apart in the spectrum and swept simultaneously. Can often be inverted so they resonate but don't remove frequencies  except those within the teeth of the comb. They often have controllable feedback. 

Can be used to make metallic or gurgling sounds, some models with a high degree of control can be used to do an array of odd things such as resonating chords out of noise or creating robot type effects.

Module Acronyms 

VCO
Stands for Voltage Controlled Oscillator; the voltage is the means used to control the pitch or note of the sound

VCF
Stands for Voltage Controlled Filter. This is the filter as described above

VCA 

Stands for Voltage Controlled Amplifier. Controls the volume of the sound and can be used as a general control in addition to the 'envelope' or for amplitude modulation

LFO 
LFO stands for Low Frequency Oscillator.An oscillator that oscillates at a low frequency. These are used to create slow fluctuations in other parameters. When applied to pitch an LFO will create a vibrato effect at the one frequency and amplitude or a siren at another frequency and amplitude.

SL  
Slew Limiter. Creates smooth transitions between voltages and can create sweeps and slides of other parameters including pitch to create a portamento effect

CV 
Control Voltage and was how older school synthesizers were controlled remotely, with patching leads.