Electro-Harmonix Slammi Plus

The Electro-Harmonix Slammi Plus is a polyphonic pitch shifter built into a wah-style foot treadle. Instead of stepping on a button and letting a knob set the interval, you rock the treadle with your foot and the pitch follows, up, down or both directions at once, across a plus or minus three octave range¹. Electro-Harmonix positions it as a pedal for whammy effects and dive bombs, bends, harmonies, cross-fades between dry and transposed sounds, and cocked pitch shifting, meaning a fixed shifted interval you dial in and leave in place like a cocked wah¹.

It arrived in 2017 as an update to the earlier Slammi, trading that pedal's motion sensor for a traditional rack and pinion treadle in a rugged, weight saving chassis¹². The Slammi Plus was discontinued in 2026, so it is now a secondhand or remaining-stock item. It launched at a US street price of $168²¹.

What it does: pitch shifting under your foot

Most pitch shifters are stompboxes: you pick an interval, step on the switch, and the shift is on or off. The Slammi Plus puts the shift on a treadle, the same physical arrangement as a wah pedal, so the amount of transposition is a continuous function of where your foot is. Rock from heel to toe and the note bends toward whatever maximum the Shift switch has set; rock back and it returns. That is what makes whammy-style dives and bends possible without a whammy bar on the guitar¹.

The shifting is polyphonic, so chords as well as single notes transpose, and Electro-Harmonix describes the transposing as flawless over the full plus or minus three octave range¹. At launch, MusicRadar reported the same claim in its news coverage, calling it "flawless, glitch-free transposing over a +/- three octave range"². Gearnews noted that packing the pedal into a large foot treadle unit made it easy to tweak on the fly³.

The controls

The control set splits into the treadle itself and the knobs and switches around it⁴.

The Blend knob is the dry/wet balance. Run it fully wet for a pure shifted signal, or back it off to blend the shifted note under your original, which is how harmony and doubling effects are set up¹.

Up, down and dual shift modes

The DIR toggle gives three modes¹:

• Up: pitch shifts upward as you sweep the treadle.
• Down: pitch shifts downward, the setting for dive bombs.
• Dual: the pedal outputs two pitch-shifted signals at once. The first follows the Shift knob as if in UP mode. The second depends on how the Pitch Mix control is configured¹.

Dual mode has two behaviors of its own. In Pitch mode, the secondary shifted signal bends at the same rate as the primary signal, so the two intervals move together as you rock the treadle¹. In X-Fade mode, the secondary signal is set by the Pitch Mix knob and does not bend; its interval choices are in half-step increments up to plus or minus one octave, and its volume decreases as you sweep the pedal from heel to toe, a cross-fade between the two shifted sounds¹. MusicRadar's launch coverage described the same behavior, noting the interval choices in half-step increments up to plus or minus one octave and the secondary signal fading out over the heel-to-toe sweep².

The 11-position Shift switch

The Shift switch is an 11-position rotary that sets the maximum transposition. It starts with D, for Detune, a shift of 17 cents that creates a chorus or doubling effect rather than a pitch change¹. From there the positions step through the musical intervals. Gearnews listed the full set at launch³:

• Detune (17 cents)
• Minor 2nd
• Major 2nd
• Minor 3rd
• Major 3rd
• Perfect 4th
• Perfect 5th
• Major 6th
• 1 Octave
• 2 Octaves
• 3 Octaves

In Dual mode with the DIR toggle set to DUAL, the Pitch Mix knob also sets the heel position's transposition in half-steps, with a range from +1 Octave to -1 Octave¹. That means the treadle can sweep between two chosen intervals rather than from unison to one interval, which is what the cross-fade and harmony settings rest on.

Slammi and Slammi Plus

The original Slammi took a different approach to foot control. It was a pitch shifter pedal with a motion sensor: instead of a treadle, you tilted or moved the pedal itself to bend pitch. MusicRadar's review described it as having a motion sensor plus four controls either side of the pedal, including a calibrate button for the sensor, a max bend control for setting the interval, and a bend up/down button⁴.

The Slammi Plus kept the idea of foot-controlled pitch shifting but moved it into a conventional wah-style enclosure with a rack and pinion operating mechanism, which Electro-Harmonix calls rugged and weight saving¹. MusicRadar's launch story framed the Plus as the Slammi updated "with a more traditional wah-style enclosure and some new functions to boot"². The Plus also added the three DIR modes and the dual-signal Pitch and X-Fade behaviors on top of the original's simpler bend arrangement.

What the press said

Gearnews, covering the launch, saw the pedal as strong value:

That comparison points at the practical alternative for most players: DigiTech's Whammy series covers similar treadle-driven pitch shifting territory at a higher price, a distinction Guitar World's later octave pedal buying guide echoed when it named the DigiTech Whammy V its pick for pitch bends. Guitar World's own launch coverage gave the Slammi Plus a US street price of $168⁵, matching MusicRadar's figure².

Where it sits in the Electro-Harmonix range

The Slammi Plus is one of several octave and pitch pedals Electro-Harmonix has made. Where pedals like the POG2, Nano POG and POG3 generate octave stacks you switch on and blend, and the Pitch Fork and Pitch Fork Plus shift fixed intervals from a compact box, the Slammi Plus is the treadle option: the interval is set on the switch, but the sweep and the drama come from your foot²¹.

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