Modulation 101: Chorus, Flanger, Phaser

The Common Thread: LFO

All modulation effects share one common ingredient: the LFO (Low Frequency Oscillator).

What is an LFO?

• A low-frequency sound wave (below human hearing)
• Controls how an effect changes over time
• Creates the "movement" or "sweep" effect

LFO Rate: How fast the LFO cycles. Measured in Hz (cycles per second).

• Slow (0.1-1 Hz): Gradual, subtle movement
• Medium (1-5 Hz): Classic modulation sound
• Fast (5-10 Hz): Intense, obvious effect

LFO Depth: How much the LFO affects the sound.

• Shallow: Subtle movement, almost transparent
• Deep: Obvious, dramatic effect

Chorus: Width and Richness

How It Works

Chorus takes your guitar signal and mixes it with a pitch-shifted copy. The pitch shifts slightly up and down, creating the illusion of multiple instruments playing together.

The Sound

• Adds width, thickness, lushness
• Makes single notes sound like chords
• Subtle on low settings, obvious on high
• Classic 1980s clean tone sound

Best Settings

• Subtle: Rate 0.5Hz, Depth 25%
• Standard: Rate 1-2Hz, Depth 50%
• Obvious: Rate 3-4Hz, Depth 75%

Best For

• Clean tone enhancement
• Pop, funk, R&B
• Adding body to thin-sounding guitars
• Stereo rigs (it doubles in stereo)

Flanger: The Sweep

How It Works

Flanger uses a very short delay (2-20ms) that's modulated by an LFO. This creates frequency "notches" that sweep through your tone, creating that characteristic "whoosh."

The Sound

• Jet-engine sweep
• More pronounced than chorus
• Can sound subtle or intense
• 1970s rock staple

Best Settings

• Subtle: Rate 0.5Hz, Feedback 30%
• Standard: Rate 1-2Hz, Feedback 50%
• Intense: Rate 3-4Hz, Feedback 70%

Best For

• Rock solos (adds presence)
• 1970s and 1980s tones
• Adding texture to leads
• Creating dramatic moments

The Feedback Control

Flanger has a unique control: feedback. This feeds the effect's output back into the input, creating more pronounced resonance. High feedback creates that intense, screaming flanger sound.

Phaser: The Swirl

How It Works

Phaser splits your signal and passes one copy through a series of phase-shifting filters. These filters create notches in the frequency response that move as the LFO modulates them.

The Sound

• Subtle swirl
• Spacey, psychedelic
• Less obvious than flanger
• Classic 1960s and 1970s sound

Best Settings

• Subtle: Rate 0.5Hz, Depth 30%
• Standard: Rate 1-2Hz, Depth 50%
• Intense: Rate 4-5Hz, Depth 75%

Best For

• Psychedelic rock
• Classic rock
• Adding space to leads
• When you want movement but not obvious effect

Comparing the Three

| Effect | Character | Best Use | Classic Setting |
|--------|-----------|----------|----------------|
| Chorus | Thick, lush | Clean tones | Rate 1Hz, Depth 50% |
| Flanger | Sweeping, jet-like | Rock leads | Rate 2Hz, Feedback 50% |
| Phaser | Swirling, spacey | Psychedelia | Rate 1Hz, Depth 50% |

Signal Chain Placement

Standard placement (after overdrive):

• Overdrive → Chorus → Delay → Reverb
• Works for most rock applications
• Chorus smooths out any harshness from overdrive

Alternate placement (before overdrive):

• Guitar → Chorus → Overdrive → Delay → Reverb
• Creates a cleaner, more refined overdrive tone
• Modulation hits your dry signal first

For fuzz:

• Fuzz → Modulation (or skip modulation)
• Fuzz can sound strange with some modulation
• Try it both ways and use what sounds best

Stereo: The Multiplier

Modulation effects shine in stereo. When you run them in true stereo:

• Chorus becomes wider (two slightly different pitch-shifted signals)
• Flanger becomes more dramatic
• Phaser becomes more immersive

Pro tip: If you have a stereo rig, modulation effects are the first ones to run in stereo. They'll give you more return on investment than any other effect type.

Choosing Your Modulation

Use Chorus when:

• Playing clean tones
• Want thickness and warmth
• Need subtle movement
• Playing funk, pop, R&B

Use Flanger when:

• Adding texture to rock leads
• Want dramatic, sweeping movement
• Playing 1970s or 1980s rock
• Need presence in a mix

Use Phaser when:

• Playing psychedelic or classic rock
• Want subtle, spacey movement
• Need something between chorus and flanger
• Creating atmospheric textures

The Bottom Line

Start with chorus on your clean tone. It's the most versatile and forgiving modulation effect. Once you're comfortable with that, experiment with flanger for rock and phaser for psychedelic textures. The world of modulation is deep—these three effects open the door.