Electro Harmonix Mod Rex Poly-Rhythmic Modulator Pedal

With Four Powerful Modulation Engines

Written by

Cian Hodge

The Electro Harmonix Mod Rex is the ultimate mix-and-match modulation pedal. Use this all-encompassing stompbox with synth or guitar to produce the most diverse polyrhythms imaginable. 

It boasts four independent modulation engines able to sync together or work separately, so you have complete control over your sound. This is the perfect pedal for experimental musicians thanks to a huge amount of controllable parameters. 


The four engines consist of Mod, Trem, Pan and Filter. Select from chorus, phaser, flanger or vibrato effects under the Mod section to shape your base modulation. These are all controlled with depth, feedback and shape dials. However the most interesting is the R. Invert, which doubles the effect for a stereo simulation.  

Move onto the Trem and Pan settings to vary the tempo and strength of pulses, or the focus of sound. These are incredibly tone-defining when used with a synth and all-out crazy applied to a guitar. These settings add a studio quality sound to recordings. The filter on the right side of the pedal changes your perception of the effects. Go from an auto-wah type sound all the way over to a lo-fi funnelling.

Sync and subdivide all of the Mod Rex's engines to a master tempo. Or each individual effect can be assigned to one of nine subdivision tempos. Use an expression pedal to further control the modulation rate. Go even deeper and explore all four LFO shapes assignable to effects. No one setting will ever sound the same.    

Intuitive design

Save up to a massive 100 presets, so you'll never forget an effect. Recall the presets easily using the digital display. Simply turn the preset dial to select an effect on the fly. 

The Mod Rex is fully MIDI compatible which is great when working with drum machines and synths. Sync up using a pulse clock so you can let everything play out in front of you, leaving your hands free to change sounds. The tap tempo feature lets you tap your foot along to the beat, keeping the Mod Rex dynamically in time with what you're playing. All modulations and LFO can adapt without hard resetting. Settings with tempo divisions bigger than or uneven with a quarter note will seamlessly stay in time.


  • Up to four simultaneous modulation sections synced in time.
  • MOD section offers a choice of Vibrato, Flanger, Chorus or Phaser
  • Standalone Tremolo, Modulated Panning and Modulated Filter sections.
  • 9 tempo subdivision options for each modulation section.
  • 4 LFO shape options for each modulation section
  • 100 storable presets
  • Full stereo input and output
  • Tap Tempo and Tempo Sync to an external device with MIDI Clock or an external pulse clock
  • Full MIDI control of all parameters and recalling of presets
  • External expression pedal input
  • External foot controller input to bank presets up and down
  • 9.6VDC/200mA power supply included
  • Dimensions in inches: 4.75 (w) x 5.75 (l) x 2.5 (h)
  • Dimensions in mm: 146 (w) x 121 (l) x 64 (h)
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