13.
Digital Signal Processing
Categories
of DSP
DSP (Digital Signal Processing) is the technique of manipulating a sound
and can be divided into 2 main categories depending upon the function.
1)
Effects DSP: The purpose is to change the colour or timbre of a sound,
e.g. Delay, Phaser, Distortion, Cut Off.
Effects DSP is covered in this chapter.
2)
Mastering DSP: The purpose is to enhance the audible quality, frequency
balance, clarity and loudness, e.g. Compressor, Limiter, Reverb and
EQ. Mastering is covered in Chapter 14
Most
DSP effects can be used in both categories, e.g. an EQ can be used to
ensure that the frequency range is balanced for mastering.
An EQ can be used to add a sweeping motion to a synth.
Effects
and Mastering DSP
The following classification of effects can be applied to any sound
source.
Name |
Description |
Compressor |
Reduces the dynamic range or the quietest point
to the loudest point |
| Distortion |
e.g. overdrive, distortion, but crusher etc |
| EQ
band pass |
Equalization
filter that passes frequencies within a certain range and rejects
all other. |
| EQ
hi pass |
Equalization
filter that passes on frequencies above a certain range. |
| EQ low
pass |
Equalization
filter that passes on frequencies only below a certain range. |
| Filter
- Stereo Spread |
a. Stereo Spread high frequencies - automation left to right
c. As above with auto filter resonance for added squelch |
| Fuzz
Wah |
Cut off and distortion, similar to a Wah Wah pedal. |
| Reverb |
Create the illusion of space by adding the ambience of different
spaces, e.g. small room, hall, and cathedral. |
| Gate |
Rhythmic amplitude modulation |
| Modulation |
e.g. Phase, Flanger, etc |
| Pan |
Left and Right or spatial surround (if you have the technology) |
| Pitch
Shifter |
Pitch
Shifter |
| Time
Stretch |
Tiny grains of a sound are looped to stretch the sound (old hardcore) |
| Vocoder |
A vocal sound is processed though ring modulation. |
Applying Filters to Instruments
Even the most simplistic sounds can be manipulated using filters to
turn them into pro studio quality.
Once a few core techniques have been established, they can be
used for Bass, Leads, Vocals and SFX.
Fig 1: A simple Bass sequence is programmed. By itself, the Saw Wave timbre is very static
and uninteresting.
Filters
Bass 1 Raw.mp3
Fig 2: A Band Pass Cut Off
filter is modulated using track automation.
Filters
Bass 2 Modulation.mp3
Fig 3: A Stereo Delay filter
is added.
Filters
Bass 3 Stereo Delay.mp3
|