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Chorus block

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Chorus block.PNG

Available on which products

  • Axe-Fx III: 2 blocks
  • FM3: 2 blocks
  • Axe-Fx II: 2 blocks
  • FX8: 2 blocks
  • AX8: 1 block

Channels or X/Y switching

  • Axe-Fx III and FM3: 4 channels
  • Axe-Fx II: X/Y
  • FX8: X/Y
  • AX8: X/Y

Chorus types and effects


  1. Digital Mono
  2. Digital Stereo
  3. Analog Mono
  4. Analog Stereo
  5. Japan CE-2
  6. Warm Stereo
  7. 80's Style
  8. Triangle Chorus
  9. 8-Voice Stereo
  10. Vintage Tape
  11. Dimension 1
  12. Dimension 2
  13. Dimension 3
  14. 4-Voice Analog
  15. 8-Voice Analog
  16. Stereo Tri-Chorus
  17. Dual Chorus

Boss CE-1

Emulating the Boss CE-1 using a LFO-driven Flanger block

Leon Todd dials in the Boss CE-1 sound, based on the 'Japan CE-2' type in the Chorus block with YouTube demo

That Pedal Show: Dan's Broken Ensemble

M@'s CE-1 emulation

Vintage tape

This type uses the tape delay algorithm from the Delay block. It sums the left and right block inputs into mono, so use caution as stereo cancellation may occur.

Dimension D

Based on Roland's SDD-320 Dimension D. Original manual

The Chorus block provides three Dimension types: Dimension 1, 2 and 3. These correspond to the modes on the original device.

The Dimension C pedal was created by Boss to produce the Dimension D effect through a pedal. In 2018 Boss released its DC-2W Dimension C pedal, an update which is part of the Waza Craft Series. YouTube

According to Guitar World, SRV used the Dimension D to add thicken his solos and still keep the tone natural.

"The Dimension Mode parameter turns on "Dimension Processing". This can be turned on in any type. However I highly recommend using the Dimension Type as it sets the correct base algorithm, LFO type, delay time, phase, etc., etc. as well as turning on the Dimension Processing. The Dimension D is really just a typical chorus. At the output, however, some special processing occurs that gives that unique sound. Turning Dimension Mode to one of the three settings engages the various aspects of that processing." source

"A Dimension D is a fairly typical chorus with some added analog processing on the outputs. The analog processing has a "normal" mode and a "boost" mode. The unit itself has four switches. These switches set the rate and the depth as well as turn on the boost mode. The switches do the following: Slow rate (0.25 Hz) and low depth, Slow rate and normal depth, Fast rate (0.5 Hz) and normal depth, Fast rate and normal depth and "boost" on. The depth is actually reduced in modes 3 and 4 to compensate for the higher rate. In the Axe-Fx this is done automatically when Auto Depth is on. Therefore I've indicated the depth as "normal" in modes 3 and 4 as the amount of pitch shift is roughly the same as mode 2. There is also an EQ that is present in all the modes on the dry signal. The LFO is a triangle wave and is 180 degrees out of phase between channels. The Dimension Mode parameter has three settings: Low, Medium and High. Low: Dry EQ off, boost off. Med: Dry EQ on, boost off. High: Dry EQ on, boost on. The Low setting has no equivalent on an actual Dimension D since the dry EQ is always active. The Dimension Type sets the LFO type, phase, Auto Depth, Hi Cut, etc., etc. and sets the Dimension Mode to Medium. With the appropriate settings of Rate and Depth you can duplicate modes 1, 2 & 3 on the actual Dimension D. To duplicate mode 4 you simply set the Dimension Mode to High. The Rates are given above. I've found a Depth of around 25% to be a good starting point. Increase or decrease to taste. The Type does NOT preset the Rate or Depth." source

(Cooper Carter) "Try the "Dimension 1" type, with Mix at 35%."

BBD algorithm

This uses an algorithm which is based on the BBD algorithm from the Flanger block. All the “Analog” chorus types use this algorithm, as well as the "Dimension 2" type: Analog Mono, Analog Stereo, Dimension 2, Dimension (and probably Japan CE-2).

"Those types use “analog” delay lines. The delay lines are virtual bucket brigade devices with the delay time controlled by a virtual oscillator. That behavior is consistent with how they would work in the real world." source


There's no dedicated Vibrato effect block or type. You can create this effect by using a 100% wet Chorus (no dry signal).

Select the Digital Mono chorus type. Keep everything at default except (source: M@):

  • Rate: as desired
  • Depth: 50%
  • Delay Time: 0.10
  • Auto Depth: High
  • Mix: 100
  • Level: -6
  • Stereo Spread: 0

Mix at 100% is not a absolute requirement. As documented here, the Vibrato mode of the venerable Boss CE-1 depends on a variable Mix setting.

More in Wikipedia


The Tri-Chorus is a very lush chorus that was very popular among studio players in the 80s and 90s. The original devices have been discontinued, but there are a few replicas.

AX8, FX8 and Axe-Fx II – Use the Chorus and/or Quad Chorus (Axe-Fx II only) effects, combined with Pitch Detune. forum discussion

Axe-Fx III and FM3 – The Chorus block has an authentic Tri-Chorus emulation type, based on a Dytronics Songbird TSC-1380. forum discussion Demonstration by Camilo Velandia

"It's just chorus. You can't do it with the II. It's a unique algorithm and there's no way to adjust the chorus block to get the same results. The III has a separate tri-chorus algorithm." source


Dual Chorus

Not available on the Axe-Fx II, AX8 and FX8.

This type has independent LFOs for the left and right delay lines. The delay lines are BBD emulations.

Creating a chorus with other blocks

The Multitap Delay block in firmware Ares can also create a lush multi-voice chorus.

The Pitch block and Plex Delay block can create a multi-voice detuning effect.

Leon Todd replicates the 8-voice chorus in Rocktron's Intellifex using the Multitap Delay

"Just use the flanger with zero feedback and modulate MANUAL. In some cases, the Flanger is now a better chorus than the chorus!" source

Position of the Chorus block on the grid

You can put the Chorus block either before (PRE) or after (POST) the Amp block. Placed PRE, the block operates as a pedal on a traditional pedalboard. Placed POST, it takes the role of a studio/rack effect.

Mono or stereo chorus

A stereo Chorus block before the Amp block will be summed to mono, so make sure it is set to mono (LFO Phase: 0) to prevent phase cancellation issues.

Some chorus types (such as 80s and Triangle) "invert" the wet sound on one side. If you're collapsing the signal to mono after the Chorus block, the wet side will completely cancel and you'll hear no chorus at all.

More information about phase cancellation


Parameters table

Parameter Axe-Fx III / FM3
Type yes
Voices yes
Rate yes
Tempo yes
Depth yes
Tri-Chorus + Dual Chorus: Left/Center/Right/Master Depth yes
Delay Time yes
Low Cut, High Cut yes
Phase Reverse yes
Drive yes
LFO Phase, Type yes
LFO2 Rate, Depth yes
Auto Depth yes
Width yes
Dimension Mode yes
Stereo Spread yes
Global Mix yes


(Axe-Fx II Owner's Manual) "Whenever the number of voices is set to more than two, the LFO type will be changed automatically to SINE. If the number of voices is greater than two and the LFO type is changed to something other than SINE, the number of voices will be reset to two."

(Axe-Fx III) "The Chorus block has up to 8 voices." source

A single chorus voice, i.e. for a Vibrato effect, can be obtained by setting LFO Phase to 0.

Stereo Spread

Values beyond +/-100% increase the apparent image beyond the stereo field.

More information about chorus

The Chorus block is explained in the Owner's Manual