Boss XS-100

The Boss XS-100 Poly Shifter is a pedal-based pitch-shifting pedal with a built-in rocker treadle, released by Boss in October 2025 at $349.99¹. It launched alongside the compact Boss XS-1 Poly Shifter, of which Boss's promotional material calls the XS-100 the "big brother"². Boss positions it as an advanced pitch-shifting workstation: a smooth onboard pedal with an integrated toe switch for linear pitch control across plus or minus four octaves, fixed pitch settings in semitone steps across eight octaves for drop tunings and capo effects, 30 memories for storing favorite setups, and TRS MIDI I/O³.

The core of the pedal is digital DSP pitch shifting built on new Boss algorithms³. Boss says the XS-100 delivers "balanced polyphonic performance that feels natural and musical across all playing styles, pickup positions, and pedal setups, with attack and tonal character fully preserved"³. A dedicated analog output mirrors the input signal, so you can keep a clean dry feed alongside the shifted one³.

A polyphonic pitch shifter with an eight-octave range

The XS-100 shifts pitch across an eight-octave range: four octaves up and four octaves down⁷. The onboard treadle gives linear pitch control across plus or minus four octaves, while fixed pitch settings in semitone steps across the full eight octaves cover drop tunings, capo effects and what Boss calls "otherworldly tones"³. A clear display handles sound editing, and 30 memories store favorite setups³.

Boss's own description of the shifting quality is direct:

Guitar World's reviewer found the shifting itself "ultra-clean"⁶. Guitar.com's Richard Purvis took a different view of the range, calling the eight octaves "overkill" and describing it as "a preposterously wide shifting range of eight octaves, four up and four down"⁷. At the end of 2025, Guitar Pedal X gave the XS-100 its GOLD award for the best new modulation, pitch, utility and multi-FX pedal of the year⁸.

The treadle, toe switch and footswitches

Real-time control comes from the smooth onboard treadle, which Boss describes as providing ultra-smooth pedal action⁴. At the end of the treadle's travel there is an integrated toe switch that introduces momentary pitch jumps with adjustable range and rise/fall time⁹¹¹⁰. Guitar Pedal X's Stefan Karlsson noted there is a further pressure sensor on the toe part of the treadle which, when depressed, triggers an additional switch function⁵.

Two footswitches sit on the body: one is typically the pitch-shifter effect on/off, the other handles core tuning and register changes, and pressing both moves up a memory by default⁵. Boss says the two footswitches can also bypass the pedal shift and quickly retune your instrument at fixed semitone steps across eight octaves¹.

For external control, the rear panel has jacks for up to two footswitches or an expression pedal¹¹¹²¹, and Guitar World's interview with Boss noted you can add a second expression pedal or a second set of footswitches¹¹. Compatible Boss accessories include the FS-5U footswitch, the FS-6 and FS-7 dual footswitches, and the EV-30, FV-500L, FV-500H and Roland EV-5 expression pedals⁵.

Power and connections

The XS-100 runs on 9V at 160 mA, with the power supply included⁶. Guitar World lists the supply as 9V AC⁶, while Guitar Pedal X's spec rundown lists 9V DC at 160 mA⁵. Because the two listings differ on whether the included supply is AC or DC, use the supplied adapter rather than assuming a standard 9V DC center-negative pedal supply will work.

The rear panel carries a TS input, a TS thru, a TS output, CTL 1/2 and EXP 2 jacks (EXP 1 is the treadle itself), 1/8 inch MIDI in and out, and USB-C⁵. The MIDI I/O supports external control and lets the pedal and footswitches send MIDI commands³. Bypass is buffered, with a BYPASS parameter selecting between analog and DSP paths, and a UNI.THRU option that passes dry signal when the effect is bypassed⁵⁶.

Where it sits in the chain

Boss says the XS-100 can be placed anywhere in your signal chain and will still follow your playing accurately, a flexibility the company contrasts with older pitch pedals that needed a specific position¹³. That makes it easier to slot in alongside overdrive, delay or reverb pedals without rebuilding the chain. For more on the category, see octave and pitch pedals.

History: Boss's first Poly Shifters

The XS-100 and XS-1 Poly Shifter were both available from October 2025, at $349.99 and $199.99 respectively¹. The XS-1 is the compact sibling; Boss's promotional material describes the XS-100 as "that lovely pedal's big brother"¹⁴². Beyond the onboard pedal, the XS-100 offers ultra-smooth pedal action and deep customization options⁴⁷¹¹, including an input for an assignable expression pedal⁴⁷¹¹.

Guitar.com's review of the XS-100 found clean shifting and strong features but a cramped control interface⁷, and its review of the XS-1 described the compact sibling as carrying the same algorithms in a simpler, cheaper pedal⁷. Guitar Pedal X called the XS-1 "the most precise pitch-shifter to date, while shifting to the extremes is always a little problematic"⁸.

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