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Boss GM-800

Boss GM-800

It’s nearly half a century since the first guitar synth became available commercially — and, boy, have they come on a long way since then!

Boss’s GM‑800 guitar synth may look a lot like their SY‑300 — both models have roughly the same form factor, colour and general control layout — but they’re very different beasts. Based around the latest generation of pitch‑tracking technology, the new GM‑800 follows the paradigm of the latter‑year GR series, specifically in that it uses a divided guitar pickup to send the individual string signals into a digital signal processor that extracts the pitch and velocity information from the notes before using it to trigger the kinds of sample‑based sounds you might expect to find in a keyboard synth. The GM‑800 can also output MIDI to control an external MIDI synthesizer or sound module, and accepts MIDI in, not only for deep parameter control but also to allow it to double as a MIDI sound module itself.


Before going further it should be noted that the connection system between the pickup system and the GM‑800 no longer uses a 13‑pin DIN connector. Instead, it employs a serial communication system that works with a standard TRS jack cable. The new compatible pickup is the GK‑5, but for those with existing GK pickups or guitars with compatible pickups built in, an adaptor called the GKC‑AD converts from the older system to the new one. This takes the form of a utilitarian metal box with a 13‑pin GK input, a serial GK output and a separate jack output that carries the standard guitar sound. Status LEDS show power and connection; power comes from an included inline adaptor. Until a connection is established between the GM‑800 and the GKC‑AD, a green LED flashes but remains solidly lit once a connection is made.

The GM‑800 launch was accompanied by that of a new GK pickup system that uses a serial connection over a standard TRS cable. The pickup is available separately, and you can also buy adaptors for older pickups.The GM‑800 launch was accompanied by that of a new GK pickup system that uses a serial connection over a standard TRS cable. The pickup is available separately, and you can also buy adaptors for older pickups.

Setup, accessed via the Menu and Page buttons, includes fine‑tuning your GK pickup options. First you select which type of pickup you have — this may be a third‑party instrument, including those with piezo divided pickups — then you need to adjust the sensitivity for each string so that they all produce a similar output for a given picking force. There’s a long list of pickups from which to choose, including third‑party systems by Graphtech, Fishman and more.

It’s very important to get the pickup setup right, as this will affect how well the instrument responds to your playing style. Set the sensitivity too high and not only will you lose out on some dynamics when picking hard, but there’s also an increased risk of triggering unwanted sounds from fingering noise. On the other hand, if you set it too low, you might not be able to reach the maximum level even when picking hard. To help with setup, a set of bargraph meters show you how much output you get from a string as you pick it. The general aim is to ensure that your normal hard picking gets the meter close to maximum without actually reaching it. There are also setup options for selecting guitar or bass, the latter requiring a GK‑5B pickup or an earlier GK bass pickup plus a GKC‑AD adaptor. As some users may have more than one GK guitar, its is also possible to create and save several different pickup settings.

The output can be mono or stereo and there are internal settings to voice the sounds for either a regular guitar amp or a full‑range speaker system (such as a keyboard amp or PA feed), which is of course preferable. The left output also doubles as a headphone output and in addition to the 5‑pin MIDI in and out ports there are two TRS Exp jacks for connecting switches or pedals. The unprocessed guitar sound has a separate output on an unbalanced jack.

There’s extensive rear‑panel connectivity, including both ins and outs for the pickup and MIDI, and USB ports for connection to a computer and to host solid‑state memory devices such as USB pen drives.There’s extensive rear‑panel connectivity, including both ins and outs for the pickup and MIDI, and USB ports for connection to a computer and to host solid‑state memory devices such as USB pen drives.

The Shape Of Progress

Although physically small, the GM‑800 has many advances over its predecessors, the most notable being its fast and accurate pitch tracking. It has a USB port for connection to a computer and while it wasn’t available for my review tests, I’m told that an editor will be available ‘imminently’. The GM‑800 can also record directly into a DAW via USB and includes the option to record the output from the divided pickup onto your DAW audio tracks, in such a way that the performance can later be replayed to trigger the sound generator of the GM‑800. This opens the door to experimenting with different sounds after making your recording. A second USB port accepts a memory stick, used for firmware updates, additional patch storage and patch transfer.

Importantly, the GM‑800 is a ZEN‑Core compatible device. The Zenology plug‑in and additional sound packs can be downloaded from the Roland Cloud using the USB connection. Essentially, you install Zenology as a plug‑in instrument (this has a load of core sounds before you even buy any expansion packs) and then, from the plug‑in, you can export your chosen sounds to the desktop and transfer them via a memory stick to the GM‑800 hardware. The process is a little convoluted, but you can transfer a large number of sounds in one go, so it is well worth doing. A GM‑800 driver must be installed on the host Mac or Windows computer, and for Mac users supported operating systems are from macOS 11 onwards.

The hardware control interface is pretty intuitive, with the four encoders below the main screen controlling what’s displayed above.The hardware control interface is pretty intuitive, with the four encoders below the main screen controlling what’s displayed above.


Dominated by a large display that shows the patch number and name when in default Play mode, the control panel is designed to be non‑intimidating. There are four different views for Play mode accessed using the Page buttons so you can also opt to view the four Tone names or the functions assigned to the footswitches for the current patch (or ‘Scene’, as Boss refer to it). Other than the Output Level control, all the knobs are rotary encoders, the four below the display accessing what’s shown above. In Play mode these can be used to change the balance of the four Tones making up the sound. Sounds can be built up using up to four layers of sample‑based sounds (Tones) plus there’s a further layer of rhythmic elements such as drum kits. There’s also an onboard selection of effects such as delay, reverb, modulation and so on, some being editable in surprising depth.

The Select encoder at the top right moves through the patches when in Play mode but has other select functions in setup mode or when editing sounds. Below are buttons for Exit, Write and Menu plus left and right Page buttons. Menu is where you find the setup details and access to editing. Illuminated buttons at the left of the display are available for the four Parts, with a further button turning the Rhythmic component on or off. When in Parts mode, selected by pressing one of them, the four buttons can be used directly to switch parts on or off and bring up a screen display allowing Tones to be selected and modified as well as accessing MFX (effects), String and Others settings such as Mono/Poly, Legato, Chromatic and Hold functions.

Scenes store the Tone layers, their settings, any effects used, control configurations and also other details, such as whether individual strings have been muted or not. The opportunities for sound editing are fairly basic so as to keep everything guitarist‑friendly, so there’s access to the essentials such as envelope shaping, vibrato, legato mode, portamento, filtering and effects, but nothing scarily deep. You can edit some of the effects in great depth if you are that way inclined but in most cases just tweaking the main parameters is all that’s needed.

A pair of Up and Down footswitches can be used to navigate the Scenes while the Control One and Two footswitches, which can operate either as latching or momentary, handle Scene‑specific functions, such as switching some of the Tones on or off or instigating a control change. Each footswitch has an associated rectangular LED.

Playability & Sounds

As shipped, there are 100 sounds ready to go and, as you might expect from a factory sound selection, there’s a bit of everything here, from orchestral and acoustic instruments to organs, pianos, EDM and bass sounds. There are also numerous drum/percussion rhythms — not every style of music will need them, but if you want to be a one‑person EDM band... The quality of sounds is excellent but inevitably only a small number of the factory Scenes are likely to fit in with your own musical leanings. Fortunately, then, it’s easy to create new sounds simply by switching out the existing Tones (samples) for something more suitable. This is easy from the front panel, but the free macOS/Windows Boss Tone Studio editor software makes it easier still, as well as making the deeper editing controls more accessible. There’s a wide range of Tones, arranged by instrument type and with a range of variations in each category. If you subscribe to the Roland Cloud or have purchased Zenology separately as a plug‑in after registering for a free account, you’ll also have a wealth of sounds available to populate your GM‑800.

By the time you read this, a Mac/Windows control app should be available — this screenshot is from a beta version shared with the author.By the time you read this, a Mac/Windows control app should be available — this screenshot is from a beta version shared with the author.

Splits can be arranged either by string (eg. bass sounds on the lower two strings and something else on the remaining four) or as you move up a string set by fret position. You can also arrange cunning layered sounds by, say, putting a bass sound on the bottom two strings, a pad sound on all the strings and adding a mono lead synth set so that one of the control switches brings in a little vibrato just to that voice. This really does create the illusion of three synths playing at the same time!

When it comes to playability, an inherent limitation with guitar synths is that, unlike keyboard synths that will sustain a note for as long as you hold a key, guitar string vibrations eventually die away to the point that no useful pitch data can be extracted. Yet, the GM‑800 can track the string pitch for a surprisingly long time and you can further extend a note by setting a longer release time so that the note continues to sound and to fade away after the guitar note has been stopped. On earlier guitar synths, this could result in erratic pitch droops, especially in pitch‑bend‑follow rather than chromatic mode, but here things seem much more solid. There are also Hold pedal functions that can be brought into play so there are plenty of options for keeping the sound going.

The new tracking algorithm definitely seems better at discriminating between a deliberate pick attack and random finger noise.

The new tracking algorithm definitely seems better at discriminating between a deliberate pick attack and random finger noise, which means there are fewer unwelcome ‘squawks’! If you accidentally strike a pinched harmonic, you may be greeted by a brief chirp or pitch swoop, but on the whole the playing feel is very natural with pitch bends and vibrato (not in chromatic mode, of course) feeling as natural as when bending conventional guitar sounds. Instruments such as pianos are best set up using chromatic mode, of course, since pitch bending is not a normal part of their sound, and the same is true of most synth pad sounds — chromatic mode will tighten up any minor tuning discrepancies, and you can set up the control switches to bring in vibrato or pitch glides as necessary. As with any guitar synth, slow‑attack sounds are the most forgiving of messy playing, while piano sounds and the like require a little more care if unintentional ‘jazz notes’ are to be avoided.


Given its realistic price and wealth of onboard sounds, the GM‑800 makes a very attractive proposition for anyone wanting to add a guitar synth to their armoury. It boasts some fairly significant technical advances and definitely feels more natural to play than previous systems. Unless you have an existing GK pickup (in which case you’ll need to buy a GKC‑AD adaptor), you’ll need to buy a GK‑5 pickup separately, which adds to the cost, but you still get a very powerful system for significantly less than I paid for my GR‑500 back in 1977!


  • Fast and accurate pitch tracking.
  • ZEN‑Core compatibility.
  • Integrates well with computer DAW software.
  • Sensibly priced.


  • Older GK pickup systems require a converter box.
  • Sound transfer from Zenology a bit clunky (but may yet improve).


The GM‑800 combines enhanced pitch tracking with access to a wide range of sounds, at an affordable price.


GM‑800 £691. GK‑5 pickup £241. GK‑5B pickup £259.99. Prices include VAT.

GM‑800 $749. GK‑5 pickup $249.99. GK‑5B pickup $299.99.

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