Questions: Subtractive Synthesis

Question 1

In subtractive synthesis, what is the primary role of the voltage-controlled filter (VCF)?

• A. Amplify the oscillator signal
• B. Remove harmonics and shape timbre
• C. Add new harmonics to the waveform
• D. Create stereo width

Answer: (B)

The VCF removes (subtracts) harmonics, transforming bright, buzzy raw waveforms into warmer, more complex tones. The filter is the central tone-shaping element of subtractive synthesis.

Question 2

What does a sawtooth wave contain that a sine wave does not?

• A. Lower fundamental frequencies
• B. Both odd and even harmonics at decreasing amplitudes
• C. A complex envelope
• D. Stereo information

Answer: (B)

A sine wave contains only the fundamental frequency. A sawtooth contains all harmonics (odd and even) at amplitudes inversely proportional to their harmonic number. This harmonic richness is what gives the filter material to subtract.

Question 3

What is an envelope generator?

Model answer: A module that modulates a parameter (like filter cutoff or amplitude) over time with four stages: Attack (time to reach peak), Decay (time to fall to sustain level), Sustain (held level while key is pressed), Release (time to fall to silence after key release).

Envelope generators shape how a sound evolves from key-press to key-release, adding dynamic character. Applied to the filter, they create tonal variation over time; applied to the VCA, they control volume shape.

Question 4

Why is resonance important in subtractive synthesis?

• A. It sets the filter color across all frequencies equally
• B. It emphasizes the cutoff frequency, adding presence and character, and at extreme values causes the filter to self-oscillate
• C. It removes frequencies more efficiently
• D. It has no audible effect on the sound

Answer: (B)

High resonance creates a ringing, emphasized band at the cutoff frequency. This is responsible for the classic 'wah' and 'sweep' sounds of analog synthesis. At maximum resonance, many filters self-oscillate — producing a sine wave pitch.