1. Subtractive Synthesis

2. Subtractive Synthesis
Subtractive synthesis is the method used to create sounds in most of the classic synths of the 1970s, such as the MiniMoog, ARP 2600 and Oberheim.
As opposed to additive synthesis, subtractive synthesis starts with a complex waveform and removes frequencies.
Most synthesizers and samplers use the basic concepts of subtractive synthesis to some extent.
Subtractive synthesis is also known as analog synthesis, though most are now virtual analog, in other words, digital.

3. Subtractive Synthesis
Signal Path
Oscillator
Source
Modifier
Filter
Amplifier
Power
Modulator
Modulator
Modulator
Dynamic- sound changes over time
Static- sound remains the same

4. Oscillators
Oscillator are the basic sound source for subtractive synthesis
Sine Wave
Dull
Triangle Wave
Hollow tube
Most synthesizers include more source waves than the basic ones listed
Modulation - frequency
Square (Pulse) Wave
Woody
Sawtooth Wave
Buzzy

5. Filters Used to remove frequencies from basic wave
Primary means of shaping a sound
Types
Low Pass filter (LPF)
High Pass Filter (HPF)
Band Pass Filter
Band Reject Filter (Notch)
Special – Formant, Comb

6. Filter Terms
Cutoff Frequency – point at which filter begins to remove frequencies
Poles – Each pole removes frequencies at a rate of 6 db per octave
Resonance – Accentuation of frequencies around the cutoff frequency

7. Low Pass Filter Removes frequencies above the Cutoff Frequency
2-pole (12 db/octave) or 4-pole (24 db/octave)
Resonance available
Creates fat sounds
Modulate – cutoff frequency, resonance amt

8. High Pass Filter Removes frequencies below the cutoff frequency
2-pole (12 db/octave)
Creates thin, nasal sounds
Modulation – cutoff frequency

9. Band Pass and Band Reject Filter
Two Cutoff Frequencies
Band Pass removes frequencies above and below the cutoff frequencies
Band Reject removes frequencies between the cutoff frequencies
Modulation – Cutoff Hz 1, Cutoff Hz 2

10. Modulation LFO – Low Frequency Oscillator Envelope Generator - ADSR
Means to change a parameter in a device
LFO – Low Frequency Oscillator
Envelope Generator - ADSR
Keyboard - Pitch
Keyboard - Velocity
Oscillators
Controllers
In advanced synthesizers virtually any device can modulate another

11. LFO Continuous device- always on Uses various waveforms or shapes
Triangle or Sine wave
Ramp up or down
Random
Modulates device parameters in time
Can be synced to tempo/meter

12. Envelope Generator (ADSR)
Attack time
Decay time
Sustain level
Release time
One-shot
Envelope generators use a trigger and gate.
The trigger is usually a depressed key.
The gate remains open and the EG remains at Sustain level until the key is released.
The envelope then moves to zero based on Release time.
Any parameter can be modulated

13. Subtractive Synthesis
Signal Path
Oscillator
Filter
Amplifier
Keyboard
LFO
ADSR