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Boss GM-800 Guitar Synthesizer System – the Synth and Software Review



MIDI guitar is reinvented. Are the results worth it?

Boss is a guitar-oriented brand of Roland, which has long been a leading force for guitar synthesis. Understanding how Boss’ latest in this category fits in – the GM-800 Guitar Synthesis System – requires some history.

Roland’s first guitar synths started with early analog systems, then they came out with PCM-based units (meaning they use digital samples) with MIDI. Their well-known VG-series processors modeled a number of acoustic and electric guitars, along with a few basses and synths.

Remember the Roland D-50 synth in the ’80s, which combined sampled attacks with analog-like sustains? The rackmount GR-50 guitar synth combined a MIDI converter and a built-in synth  that was similar to the D-110, a relative of the D-50.

Their GR-33 was the first floor unit that harbored sampled sounds, a converter to track your playing, expression pedals and footswitches, plus MIDI input and output. So it could record and play back MIDI data from a sequencer.

But MIDI playback disappeared from subsequent guitar synths, and MIDI output was secondary to the introduction of Roland’s Composite Object Modeling System (COSM). COSM can model all kinds of things, from guitars and cabinets to mics.

More recently, the Roland GR-55 combined guitar modeling and PCM-based, subtractive synthesis in a single unit, allowing interesting hybrid patches. But although it could play and record MIDI data, input was limited to System Exclusive; internal sounds could not be triggered by a sequencer. Inexplicably, pitch bend was fixed at 24 semitones.

Tracking with guitar synths was less than perfect. Even though the GR-55’s tracking seemed to be an incremental improvement over its predecessors, it took a back seat to systems by Blue Chip/Axon, Fishman, Jamstik, and others.

Most of those issues have been addressed with the Boss GM-800. 


It’s difficult to discuss the GM-800, a floor unit, without addressing the peripherals that control it. These include the new GK-5 divided pickup and the GKC-AD analog-to-digital converter, as well as the new Serial GK cable that replaces the standard 13-pin one.

What is the GKC-AD, you ask? Those invested in “legacy” controllers, such as Roland GK-3, RMC, Godin, or other 13-pin systems can now enjoy the advantages of the GM-800 through the GKC-AD; I found no perceptible difference in tracking with the GKC-AD connected to a 13-pin cable from my Brian Moore guitar and RMC pickups. 

Boss also sent us a GK-5 divided pickup, which mounts on the guitar, and connects directly to the GM-800. Missing from the GK-5, however, is a pair of switches that can be used to change patches or address assignable editing functions from the guitar. Instead, the GM-800 uses the first two footswitches for those functions. Also missing is the audio input jack for your guitar, which will require a separate signal path. 

Some may object to the absence of these features from the divided pickup. In practice, I found patch changes a bit awkward, but not difficult to get acclimated to. Removing the guitar audio from the GM-800 signal chain makes cabling more problematic. For example, the SY-1000, its predecessor, could use its internal effects to process the guitar.

Between the GK-5 and its new cable to connect the pickup and synth, and converters for older controllers and guitar synths, the system seems a bit confusing at first glance. But I came to appreciate the thoughtful flexibility and accommodation the GM-800 ecosystem provides.

As it turns out, the GM-800 can be used in a surprising number of different ways: as a MIDI converter to trigger software and hardware synths, as a synth module that can be sequenced as well as played with any MIDI controller, and as a USB device that can serve as a rudimentary audio interface.

You can record and re-amp GM-800-derived audio tracks as you would normal guitar tones.


The centerpiece of the system is the GM-800 itself. It’s a hardware, multitimbral synthesizer module and conduit for data from the GK-5, replete with a useful array of effects and routing options.

The top level of a GM-800 patch is called a Scene, whose components include as many as five sub-patches, or Tones. Tones are fully-developed, self-sufficient instruments, and they can be addressed on individual MIDI channels or globally on one channel for rich composite layers or splits.

Think of Scenes as combis, and Tones as composite patches. Programming new Tones is a bit pared down, but there are enough resources to put your own stamp on a generous variety of PCM sounds. Interestingly, you’ll find additional filters, amp modulation, and other typically internal synth components in the unit’s effects section.

A GM-800 Scene is multitimbral, comprising four synth parts and a Rhythm part: Part R. By default, the Scene presets are layered, with a few splits. How you use the parts is another matter.

You could, for example, assign a different instrument part to each channel with a drum kit on R – a typical setup for sequencing – but you can also assign and layer some of the parts and leave one part open for bass. I hate when the drums have to share the other patches’ effects, so I appreciate that each part has a dedicated multi-effects section in addition to a routing path to master effects. 

Scenes (as well as the individual tones) are tied to your playing style, which encompass the pickup settings, tweaks to the overall sensitivity of the patch to MIDI dynamics, control assignments for footswitches, and any optional pedals you might connect.

Two external control jacks are also available, each supporting up to two footswitches or an expression pedal. Control options are fairly comprehensive – and it’s fairly easy to get into the weeds.

In that regard, the unit’s worst enemy is often the documentation, which is cross-referenced across a fold-out sheet and multiple PDF files, with little view of the big picture in a complex, interdependent system. It took me several calls and a few emails to set the unit up for MIDI recording and playback, and a bit of extra head scratching before I was able to record modulation from the footswitches on the unit. Perhaps a few setup macros would help.

It’s important to note that Boss provides a download of Tone Studio, free Editor/Librarian software. Tone Studio is invaluable for setting the unit up, as well as accessing and creating new Scenes and Tone patches. I often run it in the background to tweak sounds while running them through the sequencer. Boss might consider making Tone Studio a plug-in, as Fishman and Jamstik have done with their editor/librarians.

Once past the hurdles of the scattered documentation, the GM-800 proved to be a versatile recording and sequencing tool. From the MIDI controller standpoint, tracking was exceedingly agile and clean, a marked improvement over previous units. The GM-800 handled my Roland JV-1080 synth as well as its internal sounds, plus a raft of third-party software instruments.

Tracking compared well with my Jamstik Classic MIDI guitar, albeit without Jamstik’s forward-thinking implementation of MPE, a recently-adopted addition to MIDI that allows modulation of individual notes rather than all notes. Roland/Boss touts the GM-800s greatly-improved tracking while keeping the details close to the vest. However, a discussion with a Roland technician revealed a pitch extraction system that parsed string transients, rather than waiting for several cycles and relative string stability, as earlier pitch-to-MIDI converters did. 

Outside of a DAW

Recording into a sequencer is only part of the picture. Connecting the MIDI output directly to my Roland JV-1080 synth resulted in no perceptible difference in tracking from the GM’s internal synth.

While the internal GM-800s presets have the basics done for you, you will still need to tend to necessary utilitarian drudgery, such as matching pitch-bend range and setting attack and release parameters to taste, when bringing your own synth.

I found some of the Play Feel, Low Velocity Cut, Dynamics, and other GK-5 parameter adjustments to be very helpful for fine-tuning individual patch playability when addressing external instruments.

About those sounds

Surprisingly, the majority of the GR-55 presets were overladen with distortion and reverb, with precious few enjoying the rich animation and modulation capabilities of the instrument. The release of the GM-800 marks a return to the clean, expressive timbres of earlier synths, with plenty of meat-and-potatoes sounds: fat brass; shimmering electric pianos; round, punchy bass; and warm, billowy pads.

There is a good share of raw and aggressive organs and leads, but these are more judiciously processed in overdrive, distortion, amp and speaker simulation, and other effects. In general, the patches don’t crowd the soundstage with unduly “epic” tones.

The GM-800 departs from previous Boss guitar synths in its focus on sampled sounds to the exclusion of modeling features, so no virtual guitars or synths. Instead, to expand the GM-800 palette, the synth deploys the “Zen-Core” engine, which, in common with Roland’s Fantom-series instruments and through the Roland/Boss cloud, provides for downloading a huge library of sound expansion options through a subscription service.

Sum of the parts

Naturally, there’s a whole lot more to the GM-800 than you’d want to read in a review. Last year I reviewed the Jamstik MIDI guitar here, which has equally great tracking, a downloadable software synth, and some other features – all of which are incorporated in a fully functional electric guitar.

Or… if you fork over about $200 for the GC-AD, you can combine your guitar’s output along with the GM-800’s hardware synth, which has better sounds and doesn’t need a laptop. On the other hand, if you’d like to use the new GK-5 pickup with your earlier guitar synths, for the same price the GKC-DA offers a Serial GK input, a guitar input, and a 13-pin GK output.It may or may not be a tough choice, but either way the GM-800 is worthy of consideration.

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