Boss XS-1 & XS-100 Poly Shifters

Polyphonic Pitch-shift Pedals

By Paul White

Smooth, real‑time polyphonic pitch‑shifting remains a real technical challenge, and with most pitch‑shift pedals processing artefacts are generally audible when shifting chords. Boss’ latest attempts to rise to this challenge are the compact XS‑1 and the larger, more controllable XS‑100, both based on the same underlying pitch‑shifting technology.

XS-1

Adopting the familiar Boss compact pedal format, the XS‑1 Poly Shifter is the more straightforward of the two new Boss pitch pedals, furnished with a Balance knob to blend between the dry and shifted signal, and a Shift Value rotary switch that determines how far the pitch is moved up or down. The first seven positions are semitones and the last three are octaves, with the choice of one‑, two‑ or three‑octave shifts. I found the numbers around the Shift Value control to be quite difficult to read, even when holding the pedal in front of me in daylight, so that could pose a challenge under subdued stage lighting.

A small three‑way switch sets the direction of the shift or adds detuning if left in its middle position, and the main footswitch can be set either to toggle on and off in the usual way or to operate only when the switch is held down. In detuning mode, the Shift Value knob adjusts the amount of detuning up to ±20 cents, and with the Balance control set around a quarter of the way up, this produces a very natural‑sounding chorus effect. External footswitches can be connected to switch tunings.

With just a couple of knobs and a toggle switch, what’s on offer? Set the Balance control fully clockwise and you hear only the shifted sound as set on the Shift Value dial. The first thing you notice on selecting a shifted sound is the lack of grainy artefacts. The sound is almost as smooth as using a capo, even on fancy chords, but there’s no formant correction included in the processing, so the apparent guitar body resonance will change along with the pitch‑shift. If only moving two or three semitones up/down you won’t really notice, but if you shift up by an octave the guitar body will sound smaller, almost mandolin‑like; conversely, if you shift down the body will sound larger. The harmonic content of the string is also shifted, so when shifted upwards the sound will be brighter and harmonically different from the same note played unshifted. That being the case, I’d say that for the most natural‑sounding shifts, moving up or down by just two or three semitones is safest. If you don’t mind the tonal changes, then you can go further.

As a virtual capo then, the XS‑1 is very practical, with downward shifts producing a very usable baritone guitar effect. Select an upward shift of one octave and then adjust the blend to produce an effective substitute for a 12‑string guitar. OK, so you hear octaves on all six strings, not just the lower four, but in a live context nobody is going to notice. Detune plus a suitable blend setting gives you a natural‑sounding chorus but without the obvious LFO modulation of a typical chorus pedal. It is also worth noting that any processing latency is so low as not to be significant. Some online comments suggest that the XS pedals are not great at following note bending, deep vibrato or pinched harmonics, but I tend to use all of those techniques and didn’t find any obvious issues. In my tests I placed the XS‑1 before any overdrive pedals.

With the XS‑1 being the more straightforward of the two pedals, there are some limitations. For example, I would have liked to be able to use the virtual capo mode with octaves, but here you have to choose one or the other. You can’t capo up two semitones and have octaves at the same time, so no capo’ed 12‑string sounds. Similarly, you can’t add detuning to a shift setting, only to the unison sound.

XS-100

For those with more sophisticated needs, the Boss XS‑100 Poly Shifter can store 30 presets and comes with an integrated expression pedal incorporating an assignable toe switch with the ability to pitch the note up another octave when pressed hard. This makes it significantly larger than the XS‑1 but it still maintains a reasonably narrow footprint, and the rear connectors help conserve pedalboard space. Its functions and form factor invite comparisons with the DigiTech Whammy DT, which, although far from new and not programmable, still offers cleaner pitch‑shifting than most competing pedals.

The XS‑100 has input and output jacks as well as a thru jack, mini‑jacks for MIDI in and out, and a USB‑C connector for facilitating firmware uptates. The pedal’s front panel is surprisingly sparse, with a turn/push encoder, two buttons, and two footswitches: Effect and Tune Down. Effect switches the pedal‑controlled effect on or off, but if both switches are pressed together the two switches then act as preset up and down selectors (SW mode). Tune Down brings in the downtuning or capo effect as stored in the preset, unless the switches are in SW mode. Presets may also be navigated by turning the encoder.

A small display screen covers patch selection, parameter editing, tuning functions and so on. During performance the display shows the patch number to the right, while to the left there are values for the pitching functions. Unlike the XS‑1, detuning and pitch‑shifting can run at the same time.

The Effect and Memory/Write buttons allow users to scroll through presets, access the tuner, explore the edit menus and save user patches. Memory switches between Memory mode and System Settings mode, while Effect switches between Effect mode and Editor mode. A separate CTL 1/2 EXP 2 input allows a second expression pedal to be used to control additional parameters during performance, including pitch, volume or modulation intensity. Any custom switch settings are stored along with the preset.

Offering all that the XS‑1 does and more, the XS‑100 can also handle pitch‑shifts of up to plus or minus four octaves — so your pet bat might need ear defenders. Whammy‑style pitch bends can be actioned over a user‑defined range as with the XS‑1, and there’s more flexibility in how the various pitch functions are combined.

Unlike the XS‑1, the XS‑100 caters for external MIDI control.

Verdict

The XS‑1 and XS‑100 show us that pitch‑shifting is no longer the poor relation of the pedal world. Those warbly, slightly out‑of‑tune artefacts are no longer a problem, and though the shifted sounds still don’t sound completely natural, especially at large shift values, they are sufficiently smooth and well behaved to be taken seriously. Until now the polyphonic pitch pedal market has been dominated by DigiTech, but now it has some real competition.

The compact XS‑1 brings smooth pitch shifting into the compact pedal world, while the larger XS‑100 has a built‑in expression pedal, preset handling and MIDI support for external MIDI control and integration into MIDI‑controlled rigs.

Clearly, Boss view the XS‑100 as a programmable competitor to the DigiTech Whammy DT — it even has a similar retail price! But while the XS‑100 offers more flexibility, the XS‑1’s compact size and simplicity mean it should have good potential for users who just need a virtual capo that can shift down as well as up. It can also create a detuning chorus effect, or function as a 12‑string guitar emulator. Add an expression pedal and it can produce whammy‑style pitch glides.

As commented, the XS‑1 makes a practical alternative to a capo, and as it can pitch down as well as up, it can transform a regular guitar into a baritone or even a bass, while mixing in octave shifts can also mimic 12‑string sounds. The XS‑100 can do all of that too but may be better suited to those who like the idea of a Whammy DT pedal but who need more customisable pitch effects during performance, along with user presets and MIDI integration.