How Sounds are Formed by a Synthesizer

Basic Terminology

Oscillator (the sound generator)

• The primary source of synthetic sound
• Able to produce different wave forms
• Mostly commonly: saw/sine/triangle/square/pulse/noise
• Each wave form has a distinct 'tone color' or timbre

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In 'additive synthesis', waveforms are added together to create a sound

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In 'subtractive synthesis', waveforms are edited through filtration

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Filter

• Essentially a frequency-dependent amplifier
• A sound frequency range may be set (a 'pass band')
• Only sound above the range amplified   => high-pass filter
• Only sound below the range amplified   => low-pass filter 
• If there is no such range                     => all-pass filter
• Leaves only a reduced portion of the sound

Envelope

• Allows fashioning of sounds
• e.g. Gradual onset/gradual decline
• 4 main parts to an envelope
• Attack/Decay/Sustain/Release (ADSR)

Early synthesizers used 'analogue' techniques, whereas contemporary synthesizers tend to use 'digital' techniques

Increasingly, though, both technological principles are applied in free-standing synthesizer software or 'Soft Synths'

Analogue synthesis

• Electronic signals are continuous
• More inherent noise

Digital synthesis

• Electronic signals are sent at one of two levels
• Information is quantized

Patch cords

• Allow for combining of waveforms from different generators and allow a sound 'patch' to be extended and sequentially modified