Lesson 22 — Synthesizers: The Moog-Style Architecture
A synth is not a black box. Every knob controls a real stage in the signal path.
What Is a Synthesizer?
A synthesizer builds sound from scratch instead of recording it. The most common design in classic analog synths is called subtractive synthesis: oscillators generate a bright, harmonically rich wave, a lowpass filter subtracts harmonics to shape tone, and an amplifier envelope shapes volume over time.
Every knob on a Moog-style panel controls one of these stages. The art of sound design is learning how the stages influence each other.
Oscillators (VCO)
VCO stands for Voltage-Controlled Oscillator. It produces a repeating waveform at a pitch set by the keyboard or a knob. Moog-style synths usually have two or three oscillators.
- Waveform chooses the harmonic content: sawtooth is bright and buzzy, square is hollow, triangle is soft, sine is pure.
- Octave / Range shifts the oscillator up or down by octaves.
- Detune offsets Oscillator 2 by cents, thickening the sound.
- Mix balances Oscillator 1 against Oscillator 2.
Two oscillators slightly detuned create a chorus-like thickness. The same waveform at different octaves can add bass weight or high sparkle.
The Lowpass Filter (VCF)
VCF stands for Voltage-Controlled Filter. A Moog ladder filter is a resonant lowpass filter: it lets low frequencies pass and rolls off highs above the cutoff frequency.
- Cutoff sets the border between kept and rolled-off frequencies.
- Resonance boosts the area right at the cutoff, creating a vocal or whistling emphasis.
- Envelope Amount controls how much the envelope opens the cutoff when a note is played.
- Keyboard Tracking raises the cutoff as you play higher notes, keeping tone consistent across the keyboard.
The filter is why a synthesizer can sound muffled and round, or bright and biting, with a single knob.
Envelopes (ADSR)
An envelope is a control shape, not an audio signal. It tells another stage how to behave over time. On a Moog, the same envelope often shapes both the filter cutoff and the amplifier volume.
- Attack — time from silence to peak.
- Decay — time from peak to sustain level.
- Sustain — level held while a key is pressed.
- Release — time to fade after the key is released.
A short attack makes a punchy bass. A slow attack turns the same oscillator into a swelling pad. The envelope amount knob decides how strongly the filter follows that shape.
LFO & Modulation
LFO stands for Low-Frequency Oscillator. It moves a parameter up and down slowly enough to be heard as motion instead of pitch.
- LFO → Pitch creates vibrato.
- LFO → Filter creates a rhythmic wah or sweep.
- Rate is how fast the LFO cycles.
- Amount is how far the parameter moves.
The LFO is the simplest way to make a static synth sound alive.
MONAKAI MOOG-LAB
Below is a working Moog-style synthesizer. The knobs mirror the sections you just read. Flip the schematic switches to reroute the LFO and see the active signal path glow.
Oscillators
Filter
Envelope
LFO & Glide
Master
Click keys or use keyboard row A–K to play. Sharps are W, E, T, Y, U.
Interactive Signal Schematic
Flip the switches to reroute modulation. Active routes glow. The colored lines match the key below.
🎧 Monakai Pro Tip
A Moog-style synth is just voltage moving through blocks: oscillators make raw pitch, the filter carves tone, and the envelope shapes time. If you can hear those three stages, you can program almost any subtractive synth.
Key Takeaways
- A subtractive synth starts with oscillators, then shapes sound with a filter and envelope.
- Oscillators create the raw pitch and timbre.
- Filters remove frequencies to shape tone.
- LFOs add movement by modulating pitch, filter or amplitude over time.
Practice This
Open your DAW and apply one idea from this lesson to a 16-bar loop. Don't worry about making a full track — just experiment until the concept feels natural in your hands.
Try Monakai's free VST3 plugins to hear these ideas in action, and check the music production blog for more tips.