At a glance
| Property | Chorus | Flanger | Phaser |
|---|---|---|---|
| How the copy is changed | Delayed, with the delay moving | Delayed, with the delay moving | Phase shifted by allpass filters |
| Typical delay | About 10 to 30 ms | About 0.5 to 10 ms | None |
| Notches | No fixed pattern | Dozens, evenly spaced | A few, wide and uneven |
| Feedback | Little or none | Often, for a metallic ring | Often, called resonance |
| Sounds like | Several players at once | A jet plane passing | A smooth, hollow whoosh |
| Best for | Clean guitars, pads, backing vocals | One riff, a drum break, a transition | Rhythm guitar, keys, slow movement |
How modulation effects work
Chorus, flanger and phaser are all modulation effects. Each one takes a copy of your sound, changes it slightly and mixes it back in with the original. The changing is done by an LFO, a low frequency oscillator: a wave too slow to hear, usually between about 0.1 and 10 Hz, that turns a setting up and down for you. Almost every unit gives you two knobs for it. Rate sets how fast it cycles, and depth sets how far it moves the setting.
What makes them interesting is the moment the copy meets the original. If the copy arrives a few milliseconds late, some frequencies line up and get louder, while others arrive exactly out of step and cancel. Those cancelled frequencies are called notches, because on a spectrum they look like sharp dips. When the LFO moves the delay, the notches move, and you hear a sweep.
Where the three part company is in how the copy gets changed. A chorus delays it by roughly 10 to 30 ms. A flanger delays it by under 10 ms and usually feeds some of it back into itself. A phaser runs the copy through filters that shift the phase of each frequency by a different amount, with no delay at all. Those differences decide how many notches you get and where they sit, and that's most of what you hear.
Reading the lab
The cards along the top choose the effect, and each one remembers its own settings, the way three pedals on a board would. On a keyboard, 1 to 4 flip between them.
The wide screen under the cards shows the whole loop, with time running left to right and frequency running up the side. Each spot compares the sound after the effect with the original. An even colour means that frequency came through unchanged, a dark band means it's being cancelled, and ivory means it got louder. That makes the three effects easy to tell apart at a glance: a flanger draws lots of dark bands that move together, a phaser draws two or three broad ones, and a chorus leaves a faint, shifting texture with no clear bands at all.
Below it on the left is the LFO itself, recorded while the loop was rendered. For chorus and flanger it shows the delay time in milliseconds; for the phaser, the frequency of its middle notch. The dot is the moment you're hearing, and with Spread turned up a dashed line shows the right channel.
The middle screen is the spectrum at that moment. The faint line is the original, the coloured shape is the sound after the effect, and the white line is the shape the effect has right then, with its notches marked along the bottom. The readout in its corner gives the current delay or the notch frequencies.
The panel on the right explains what your settings are doing, using numbers measured from the loop. The lab also plays every option at the same loudness as the original, so a setting can't win just by being louder. Use your own sound if you like: upload a file, or press Record and play something for eight seconds. Nothing leaves your device.
What is a chorus effect?
Chorus makes one instrument sound like several playing together. When two violinists play the same line they're never exactly together: one is a few milliseconds behind, and their tuning drifts apart by a few cents. A chorus effect copies that with duplicates of the sound delayed by about 10 to 30 ms, with the LFO slowly moving each delay up and down.
Moving a delay changes the pitch of the copy. While the delay is getting longer, the copy is being stretched and plays slightly flat; while it's getting shorter, it plays slightly sharp. It's the Doppler effect, the same thing that makes a passing siren drop in pitch. In the lab's chorus, a depth of 40% moves each delay 4 ms either side of 20 ms, and at 0.75 Hz that bends the pitch of each copy by up to about 32 cents, roughly a third of a semitone.
The delays are long enough, and moving enough, that the copies never settle into a clean pattern of notches. What you hear is thickness and shimmer, with no obvious sweep. The lab uses three copies with their LFOs a third of a cycle apart, so they're never all moving the same way at once. Roland built a chorus into the Juno-60 synth, switched by two buttons marked I and II, and plenty of synths since have a chorus switch of their own.
What is a flanger?
A flanger uses a single copy delayed by a very short time, from under a millisecond up to about 10 ms, swept by the LFO. The name comes from tape. Engineers played the same recording on two tape machines at once and slowed one by pressing a finger on the flange, the rim of its tape reel, so the two drifted in and out of time with each other. The swooshing effect on Small Faces' “Itchycoo Park” from 1967 was done with tape this way.
At delays that short, the copy cancels a whole series of frequencies. A frequency cancels when the delay equals half of one of its cycles, or any odd number of halves. So a 1 ms delay cuts notches at 500 Hz, 1.5 kHz, 2.5 kHz and every 1 kHz above that. At 5 ms they start at 100 Hz and sit 200 Hz apart. Drawn on a spectrum the pattern looks like the teeth of a comb, which is why it's called a comb filter, and the comb filtering lesson covers it in more detail.
When the LFO sweeps the delay, the whole comb slides up and down at once. The notches are evenly spaced, so they cut into the harmonics of a note in a regular pattern, and that's where the hard, metallic character of a flanger comes from.
Flanger feedback
Most flangers have a feedback control, sometimes called regeneration, that sends some of the delayed signal back into the delay. The frequencies between the notches build up into narrow, ringing peaks. In the lab, 70% feedback at a 50% mix puts about 15 dB between the peaks and the notches, and the sweep gets sharper and more metallic. Without feedback the notches are deeper but there are no peaks, so the sound is smoother and more hollow.
What is a phaser?
A phaser sweeps notches through a sound too, using a chain of filters where a flanger uses a delay. An allpass filter passes every frequency at the same level and shifts its phase: low frequencies hardly at all, high frequencies by up to half a cycle, with the halfway point at a frequency you choose. Mix that copy with the original and anything that comes out exactly half a cycle shifted cancels.
One of these filters on its own never quite gets to half a cycle, so phasers chain several together. Every two stages give you one notch, which means a four-stage phaser has two notches and the six-stage one in this lab has three. With the middle notch at 1 kHz, the lab's three sit at about 270 Hz, 1 kHz and 3.7 kHz. The LFO moves the filters' halfway point up and down, and all three notches slide together.
That spacing is the reason a phaser sounds different from a flanger. A flanger with a 1 ms delay has 18 notches below 18 kHz, evenly spaced; the phaser has three, they're wide, and they follow no pattern that lines up with the harmonics of a note. The sweep comes out smooth and hollow. Phasers often have feedback too, sometimes labelled resonance, and it does the same job as on a flanger: it lifts the peaks between the notches so the sweep sounds more vocal.
How to tell chorus, flanger and phaser apart
Listen for a sweep first. If the sound gets thicker and wider and nothing seems to rise and fall, it's a chorus. If there is a sweep, listen to its edge. A flanger's comb gives it a hard, metallic quality, and with feedback you can often hear something like a pitched tone gliding up and down inside the sound. A phaser's sweep is softer and rounder, closer to someone saying "oo" and "ah" very slowly.
Noisy sounds make the difference obvious. Cymbals, hi-hats, distorted guitars and pink noise all have energy right across the spectrum, so every notch has something to cut into. That's why flanged drums are such a recognisable sound, and it's why the lab has a noise source.
The controls
Most plug-ins and pedals for these effects share the same handful of controls, whether it's a stock plug-in in Ableton Live or Logic or a pedal on the floor. The names vary a little, and the jobs are the same.
Rate
Rate is the speed of the LFO in hertz, which is cycles per second. At 0.25 Hz a full sweep up and back takes four seconds; at 2 Hz it takes half a second. Flangers and phasers are usually set slow, somewhere between 0.1 and 1 Hz, so you hear each sweep. Chorus works well a little faster, from about 0.3 to 1.5 Hz. Push any of them past about 4 Hz and they turn into a warble.
Rate also affects pitch on the two delay-based effects. The faster the delay moves, the further the pitch bends, so doubling the rate of a chorus doubles its pitch drift. The lab rounds the rate to a whole number of cycles per loop, so on the 8 second strings and chords loops it moves in steps of 0.125 Hz, which is one cycle every four bars at 120 BPM.
Depth
Depth sets how far the LFO moves things. In the lab's chorus, 100% swings each delay between 10 and 30 ms. On the flanger, 100% sweeps the delay from 0.5 ms up to 10 ms, which takes the lowest notch from 1 kHz down to 50 Hz. On the phaser, 100% moves the middle notch across five octaves, from 160 Hz to about 5 kHz.
On a chorus, depth and rate together decide the pitch drift. In the lab, 40% depth at 0.75 Hz bends each copy by about 32 cents; double the depth and it's about 64 cents, which is where a chorus starts to sound seasick.
Feedback
Feedback sends part of the effected copy back into its own input. It's the control that does the most to a flanger or phaser and the least to a chorus, where it's normally left at zero. On a flanger, 50 to 80% gives the jet-plane sound. As it gets close to 100% the peaks ring on and on, which is why the lab stops at 90%.
Mix
Mix sets the balance between the original and the copy, and it does more here than on most effects. The notches only exist because the two cancel, so the deepest ones come at 50%, where the copy and the original are the same level. At a 25% mix the same notch only goes down about 6 dB. At 100% there's nothing left to cancel against: a flanger with no feedback turns into a slight pitch wobble, and a phaser sounds almost dry, because an allpass filter on its own doesn't change the level of anything.
Chorus pedals and guitar phasers often have no mix knob at all, because they're fixed at an even blend.
Spread
Spread, sometimes called stereo phase or width, sets the LFOs on the left and right out of step with each other. At 100% in the lab they're half a cycle apart, so when the left delay is at its longest the right one is at its shortest. Each speaker hears a different moment of the sweep, and the sound gets wider. The correlation figure in the lab's panel measures it: 1 means the two sides are identical, and lower numbers mean they're more different. This is how most stereo choruses get their width, and the stereo width lesson explains what that does to a mix.
When to use which
| Job | Chorus | Flanger | Phaser |
|---|---|---|---|
| Thicken a clean guitar or a pad | Best | Too obvious | Works, set slow |
| Movement on a rhythm part | Very little | A lot | Good |
| A big sweep on a riff or drum break | No | Best | A softer version |
| Width in stereo | Best | With spread | With spread |
| Backing vocals | Good, kept light | As a special effect | As a special effect |
| A lead vocal | Very light, if at all | One phrase at most | One phrase at most |
Using them on guitars, synths and vocals
Guitars
Clean electric guitar is where chorus gets used most. Chords and arpeggios played through a chorus at around 0.5 to 1 Hz, with a low depth and an even mix, get a wide shimmer that sits behind a vocal without crowding it. Phasers suit rhythm parts, especially in funk and rock, where a slow sweep keeps a repeated part moving. A flanger is the most obvious of the three, so it tends to come in for one riff or one section, where the sweep is the point. Choose the Guitar loop in the lab to try all three on a guitar part.
Synths
Pads and polysynth chords take chorus very well, because it does the same job as detuning several oscillators against each other, which the unison and detune lesson covers. A slow phaser on an electric piano or a string synth gives it a gentle, rolling movement. A flanger with high feedback on a bright synth lead or a noisy sound effect gives you the full jet-plane sweep, which can work well going into a drop.
Vocals
Vocals are the place to be careful. A lead vocal with obvious chorus sounds out of tune, because the copies drift in pitch against the singer. If you want width on a lead, a very light chorus on a send, mixed well under the dry vocal, is safer than an insert. Backing vocals and doubles can take a lot more. A flanger or phaser on a single word or phrase makes a good special effect, and automating the mix up for that moment and back down afterwards keeps the rest of the vocal clean.
Drums and whole mixes
Drums show a flanger off better than almost anything, because hi-hats and cymbals are noisy enough for the comb to cut into every frequency. Flanging a drum break, or a whole mix for a bar or two before a drop, is a long-standing trick in dance music.
How to set up a chorus, flanger or phaser
- Choose the effect for the jobChorus to thicken and widen, flanger for a strong metallic sweep, phaser for a softer one. The table above is a good place to start.
- Start with an even mixSet the mix to 50%, or use the effect on a send and bring the return up to a similar level, so the notches are as deep as they get while you set everything else.
- Set the rate slowBegin around 0.2 Hz for a flanger or phaser and 0.5 Hz for a chorus. If your plug-in can sync to tempo, one cycle per bar or every two bars keeps the sweep in time with the song.
- Bring the depth up until you hear itThen back it off a little. On a chorus, listen for the point where the pitch starts to sound wobbly and stay under it.
- Add feedback lastFor a flanger or phaser only. Raise it until the sweep has the ring you want; on a chorus, leave it at zero.
- Check it in context and in monoListen in the full mix, then switch your master to mono. If the part drops in level or sounds hollow, turn the spread or the depth down.
Starting settings
These are places to begin, chosen so the effect is clearly there. The depth figures are for the lab, so on other plug-ins treat them as low, medium or high.
| Use | Rate | Depth | Feedback | Mix |
|---|---|---|---|---|
| Chorus on a clean guitar | 0.5 – 1 Hz | 20 – 40% | 0% | 30 – 50% |
| Wide chorus on a pad | 0.2 – 0.6 Hz | 30 – 50% | 0% | 50%, spread up |
| Jet flanger | 0.1 – 0.3 Hz | 60 – 90% | 50 – 80% | 50% |
| Gentle flanger | 0.2 – 0.5 Hz | 30 – 60% | 0 – 30% | 30 – 50% |
| Phaser on rhythm guitar | 0.3 – 1 Hz | 50 – 80% | 20 – 40% | 50% |
| Slow phaser on keys | 0.1 – 0.3 Hz | 60 – 90% | 0 – 30% | 50% |
Common mistakes
Too much depth on a lead part
Pitch drift that sounds lush on a pad sounds out of tune on a melody. A chorus moving 5 ms either way at 1 Hz bends the pitch by about 54 cents, more than a quarter of a tone. On leads and vocals, keep the depth low enough that you notice the width before the wobble.
Leaving the original out
A chorus, flanger or phaser on an insert with its mix at 100% has nothing to cancel against, so most of the effect disappears. If a plug-in seems to be doing nothing, check the mix first. On a send, set the plug-in itself to 100% wet, since the dry signal is already in the channel.
Forgetting about mono
Wide stereo modulation can sound huge on headphones and lose level when the mix is folded down to one speaker, because the left and right partly cancel. Plenty of people still hear music on a single phone or kitchen speaker, so check every wide effect in mono. The mono compatibility lesson shows what to listen for.
A rate that fights the tempo
A sweep at a rate that has nothing to do with the song lands somewhere different in every bar, which can sound unsettled on a loop-based track. At 120 BPM a bar lasts two seconds, so 0.5 Hz is one sweep per bar and 0.125 Hz is one every four. Most plug-ins let you set the rate in note values to do this for you.
Training your ears to tell them apart
The quiz under the lab plays the current sound through a chorus, a flanger or a phaser with randomised settings. It covers the screens and the controls and matches the loudness, so nothing gives the answer away except the sound itself. Eight rounds take a few minutes, and your best score is saved in your browser. Start on the strings, then try the guitar and the chords; flanger and phaser are the closest of the three, so listen for that metallic edge.
Questions people ask
Is a phaser the same as a flanger?
No. Both sweep notches through a sound by mixing a shifted copy with the original. A flanger shifts the copy with a short delay, which cuts dozens of evenly spaced notches, and a phaser uses allpass filters, which cut only a few. That's why a flanger sounds metallic and a phaser sounds smoother.
Which is best on guitar: chorus, flanger or phaser?
Chorus, if you want one that works on most parts. It thickens clean chords and arpeggios without drawing attention to itself. A slow phaser suits rhythm parts in funk and rock, and a flanger is obvious enough that it's usually kept for one riff or one section.
What's the difference between chorus and vibrato?
Vibrato is the pitch wobble on its own: a moving copy of the sound with none of the original mixed in. Chorus mixes moving copies with the original, and the small differences in pitch between them are what make it sound thick.
Should chorus be stereo?
Usually, because most of a chorus's width comes from the two sides moving differently. Check it in mono, though. When the left and right are added together, a wide chorus can partly cancel, and a pad can lose level or thin out on a phone speaker.
What does the rate knob do on a phaser?
It sets how many times a second the notches sweep up and back down. Somewhere between 0.1 and 0.5 Hz gives a slow sweep you hear as a whoosh, while 3 to 6 Hz turns into a fast warble.
Where do chorus, flanger and phaser go in an effects chain?
There's no fixed rule, but a common order on guitar is distortion, then modulation, then delay and reverb. A phaser before the distortion is popular too. Put any of them after a reverb and the reverb tail gets swept as well.