Chorus is a modulation effect that mixes a signal with one or more delayed copies whose delay time constantly changes, so the copies drift slightly in pitch and timing against the original. Among audio effects, it imitates the natural thickness of several singers or players performing the same part, which is where the name comes from.
Chorus is used on guitars, synthesizers, electric pianos, bass and vocals to create width, movement and shimmer. It belongs to the same family of time-based modulation effects as flanger and phaser, but it works with longer delays and gentler modulation, which gives a smoother and less metallic sound.
How the chorus effect works
A chorus works by passing the signal through a short delay line whose delay time is varied by a low-frequency oscillator (LFO). When the delay grows, the copy is stretched and its pitch drops slightly; when the delay shrinks, the pitch rises. Mixing this moving copy with the dry signal produces gentle detuning and timing variation.
Typical chorus delays sit between about 10 and 30 ms, long enough to avoid strong comb filtering but short enough that no distinct echo is heard. The LFO usually runs between 0.1 and 3 Hz, and the modulation depth sets how far the delay swings, which in turn controls the amount of pitch variation, usually only a few cents.
The table explains the main chorus controls and their typical ranges.
| Parameter | Typical range | Audible effect |
|---|---|---|
| Base delay | About 10 to 30 ms | Sets how separate the copies sound |
| Rate (LFO speed) | About 0.1 to 3 Hz | Slow shimmer or fast warble |
| Depth | A few milliseconds of swing | Amount of detuning |
| Mix | 20 to 50 percent wet | Balance of dry and effected sound |
| Voices | One to eight copies | Thicker ensemble sound |
| Feedback | Zero or low | Adds resonance, rarely used in chorus |
Chorus compared with flanger, phaser and doubling
Chorus differs from its neighbors mainly in delay length and feedback. Shorter delays with feedback produce a flanger, filter-based phase shifts produce a phaser, and unmodulated or randomly varied delays create doubling effects.
| Effect | Mechanism | Typical delay | Character |
|---|---|---|---|
| Chorus | Modulated delay mixed with dry signal | About 10 to 30 ms | Wide, lush, smooth |
| Flanger | Modulated delay with feedback | About 1 to 10 ms | Sweeping, jet-like, metallic |
| Phaser | All-pass filters create moving notches | No fixed delay line | Swirling, vocal-like |
| Vibrato | Fully wet modulated delay | Short | Pitch wobble without the dry signal |
| Doubler | Slightly offset, varied copy | About 20 to 50 ms | Sounds like a second performance |
The boundary between chorus and flanger is not strict, and many units cover both. A useful rule is that chorus aims for thickness without an obvious sweep, while a flanger deliberately makes the moving comb-filter notches audible.
Variants and implementations
Chorus exists in analog, digital and multi-voice forms, and each has a recognizable sound. Classic analog chorus pedals and synthesizers used bucket-brigade delay chips, which add slight noise and high-frequency loss that many players consider part of the character.
| Variant | Description | Typical use |
|---|---|---|
| Analog chorus | Bucket-brigade delay with LFO | Guitar pedals, vintage synthesizers |
| Digital chorus | Clean, precise delay modulation | Studio plugins and multi-effects |
| Stereo chorus | Opposite modulation in left and right | Widening mono sources |
| Ensemble or multi-voice chorus | Several voices with different LFOs | Strings and pad sounds |
| Dimension-style chorus | Subtle, carefully balanced stereo modulation | Gentle widening without obvious wobble |
Stereo chorus is especially popular because it widens a mono instrument across the stereo field. One channel receives the modulated copy in one phase of the LFO and the other channel in the opposite phase, which creates constant movement between the speakers.
Using chorus in a mix
Chorus works best when it is used for a clear purpose, such as widening a clean guitar, softening a synthesizer pad or adding sparkle to a backing vocal. On lead elements, a little chorus usually goes a long way.
| Source | Suggested approach | Reason |
|---|---|---|
| Clean electric guitar | Slow rate, moderate depth, stereo | Classic shimmer and width |
| Bass guitar | Chorus only above about 200 Hz | Keeps low end solid and centered |
| Synth pad | Multi-voice, slow rate, higher mix | Lush, wide texture |
| Backing vocals | Subtle depth, low mix | Thicker blend without wobble |
| Lead vocal | Very little or none | Detuning can reduce clarity |
Many engineers place chorus on an auxiliary send rather than directly on the track. This allows the effect to be filtered, panned wide and balanced independently, while the dry signal stays focused in the center.
Common problems with chorus
The most common chorus problems are poor mono compatibility, seasick pitch and blurred low frequencies. Because chorus mixes signals with changing time offsets, some frequencies cancel when the stereo image is folded to mono.
- Check the mix in mono, especially for stereo chorus on important parts.
- Lower the rate or depth when sustained notes sound out of tune.
- Filter the low end of the effect so bass and kick remain stable.
- Avoid stacking chorus on many tracks, which makes the whole mix sound vague.
In simple terms
Chorus makes one sound behave like several sounds playing together. When a group of people sings the same melody, nobody is perfectly in time or in tune, and those small differences make the group sound full.
The chorus effect creates copies of a sound that drift slightly in timing and pitch, then blends them with the original. The result is wider and softer, like turning one guitar into a gently shimmering group.
A practical example
A producer records a clean electric guitar part for a slow indie song, but the part sounds thin and narrow in the mix. The guitar was recorded in mono with one microphone, and doubling it would require another session.
The producer sends the guitar to an auxiliary bus with a stereo chorus set to a rate of about 0.6 Hz, moderate depth and a base delay of about 18 ms. A high-pass filter at 250 Hz on the chorus return keeps the low end tight, and the return is mixed about 8 dB below the dry track.
The guitar now fills both sides of the stereo field while the dry part stays centered. A mono check shows only a slight change in tone, so the effect is kept for the final mix.