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Synth Pedals for Guitarists, Part 1

Marty Cutler

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Electric guitarists and bassists can play synthesizer with these synth pedals — no MIDI required.

Why has the guitar synth been slow to catch on? You’ll find no shortage of excuses: proprietary cables or guitars, confounding new protocols, latency, and the fact that converting the guitar or bass to a digital language can be as oblique as converting voice to text on your phone. In the past few months, a new generation of guitar synthesizers—primarily stompboxes—bestow instant sonic gratification, often while steering completely around MIDI.

You can find quite a few gateways to guitar synthesis, even if you avoid MIDI entirely. For instance, the Line 6 Helix, Fractal Axe FX, and even the pocket-sized Korg Pandora effects processors offer a playable monophonic synthesizer.

What exactly constitutes a guitar synth is almost as thorny as the question, “What is jazz?” Pinning down a definition gets even more complicated as we look at floor units and stompboxes. The garden-variety subtractive synthesizer has oscillators, a filter, and an amplifier. To varying degrees, a synth also has modulation capabilities, with LFOs, envelope generators, a mixer, amplitude modulation, frequency modulation, and so on.

Guitar synths, especially the stompbox varieties, have at least some of these features. For example, the Boss SY-300—arguably the first floor unit to claim polyphonic synthesis from a non-divided signal—boasts three oscillators. Technically speaking, though, it has no actual oscillators—at least, not in the sense of digitally or voltage-controlled waveforms. It’s easy to assess these devices as guitar processors. Nevertheless, the results sound markedly electronic, and playing any of these devices renders such distinctions moot.

Vive La Difference!

These guitar synths don’t replace a MIDI guitar. Because MIDI guitars can control any synthesizer equipped with MIDI ports, they offer an infinitely broader palette of sounds than any current pedal can offer. Also, of course, you can record MIDI data into a sequencer, edit individual notes, and change the sounds or even the synthesizer after you have recorded tracks.

Nonetheless, the guitar synths reviewed here are tremendously attractive to the live string player, offering virtually instant tracking that’s mostly glitch-free, with uncomplicated polyphony, sound editing, connectivity, and controls. Still, as in any synthesizer, envelopes will affect the synth’s performance, and pads are rarely a good choice for Mahavishnu-style solo excursions. Glitches are always possible; if your technique isn’t clean, guitar synths tend to amplify clams or unintentionally brushing strings.

Synth Pedals for Guitarists

Polyphonic synthesizer output from a monophonic signal is a relatively recent development in guitar synthesis, and as such, manufacturers are reluctant to share their secrets. Nevertheless, it’s probably safe to presume that polyphonic pitch detection stems from the same sources that led to the development of Celemony Melodyne, an audio-editing program that lets you edit individual notes of a polyphonic audio track.

Jam Origin is a Mac/Win/iOS app that converts MIDI data from monophonic audio input and spits out polyphonic MIDI. One of the synthesizers reviewed here is monophonic, but as a polyphonic effects processor, it can process the guitar signal through much of its synth architecture, and its controls and connections are more complex than most.

Each synth in this roundup offers unique results and sounds. All are worthy of your attention. This month I’m covering four effects pedals, three of them from Electro-Harmonix, that permit guitarists and bassists to produce synthesized tones. Next month I’ll cover several more in Part 2.

Boss SY-1 ($199.99)

Boss and Roland collectively hold the longest history in the development of guitar synthesizers. In 1977, Roland released the GR-500, the first guitar synth paired with a modified guitar that introduced the first divided pickup. More recently, Roland debuted the GR-55, a floor unit whose fully programmable, dual-oscillator, sample-based synth lets you layer with a variety of modeled guitars and synthesizers. Shortly thereafter, the Boss GP-10 bestowed a MIDI controller and virtual guitar that—despite the absence of a PCM synth—functionally got the jump on the GR-55, with the inclusion of programmable independent pitch-bend pedal settings (a bit like a pedal steel, but with a single pedal), a couple of new models, and the ability to switch synth models between poly and monophonic settings.

Not long afterward, Boss introduced the SY-300 Guitar Synthesizer, a polyphonic synth with three oscillators, envelope generators, and other modulation capabilities—all accessed with a standard guitar cable. All the SY-300’s sounds are eminently programmable, with banks of online patch libraries accessible via the unit’s Tone Studio editor for your computer. 

Boss Synth Pedal


In August, Boss unveiled the SY-1, a polyphonic guitar synth that has a typical stompbox form factor, which in some ways ups the ante of the SY-300. The SY-1 strikes a thoughtful balance between ease of use and adaptability. 

A pair of concentric knobs lets you balance synth and guitar levels individually. Another pair of concentric knobs labeled Tone/Rate and Depth control those parameters, but they also control parameters such as transposition, resonance, and filter frequency, depending on which preset you select. The SY-1 offers nine categorized banks of presets: two lead banks, pads, bass, strings, organs, bells, and two banks of special-effects patches and sequenced synth riffs. Each bank offers 11 variations on its theme that you access with a knob to the left of the Type knob.

In addition to 1/4-inch input and output jacks, the unit has a separate send and return for processing the guitar signal externally. The output jack passes signals from both the synth and guitar. Another 1/4-inch jack accepts a footswitch or expression pedal, taking over the patch’s modulation assignments—a much easier operation than kneeling down and squinting at the knobs. The built-in pedal switches from the guitar signal to the synth, and holding it down will sustain the patch for as long as it’s depressed.

I found many reasons to get excited about this pedal. With few exceptions, the patches convey the sense that they were designed for guitarists rather than keyboard players. All the patches bend smoothly, and envelopes respond dynamically without ever conveying an unwieldy (and often glitchy) retriggered feel. The SY-1 should be a runaway success among guitarists and bassists looking for radically new sounds.

Electro-Harmonix 9 Series Pedals

Electro Harmonix (EHX) may have more guitar synthesizer pedals on the market than all other manufacturers combined. The company’s 9 Series is about as close to the goals of guitar-controlled synthesis as you can get from a stompbox. Each unit focuses on a different instrument category. I spent time with their organ, Mellotron, and synthesizer pedals. They also make pedals that allow guitarists to emulate electric pianos, basses, and additional organs. All are the same size and offer similar, uncomplicated control arrangements. All are a gas to play.

B9 ($221.30)

One of the earliest attempts that allowed guitarists to emulate other instruments was the Vox 251 Guitar Organ, in which Vox implanted the guts of its popular Continental Organ into a somewhat abstract-looking guitar body. Notes were triggered when the strings made contact with a segmented array of frets. As such, these early attempts at guitar synthesis were awkward to play.

B9 Synth Pedal

The Electro-Harmonix B9 Organ Machine does away with all that, allowing you to simply plug in your 1/4-inch guitar cable, connect to an amp, and play truly convincing organ sounds with the added benefit of smooth and musical guitar articulations, such as hammer-ons and string bends.

The B9 replicates (but is not limited to) Hammond organ tones. As with the other pedals in the 9 Series, it derives its sounds by polyphonic pitch shifting and voicing the strings into new sounds, a technique EHX uses on a number of their synth emulations. The pitch shifting in this case functions in the same way drawbars add additional frequencies to an organ. The results are startlingly realistic.

The B9 supplies nine different organ presets you dial up with an easy-to-see white knob. Modulation types (chorus, tremolo, or vibrato) vary depending on which organ preset you choose. Next to the Dry signal and Organ volume knobs is the Mod knob for controlling modulation rate. The Click knob either produces a key-click effect or controls modulation depth, also depending on the preset. For example, the Click knob increases tremolo depth for a pipe-organ emulation and vibrato depth for a Vox Continental-type preset.

Like every pedal in the 9 Series, the B9 has a single 1/4-inch jack that accepts a mono signal from a guitar, bass, or other stringed instrument. It also has a 1/4-inch output for the wet (synthesized) signal and another for the dry signal. B9’s wet output passes both signals but lets you balance the two with independent knobs for each signal; that can come in handy when your output options are limited to a single amp or input.

Mel9 ($221.30)

Comparatively speaking, emulating organs using pitch shifting and filters seems like a walk in the park when compared with emulating a classic keyboard that played tape recordings of “real” instruments. Mel9 emulates nine classic Mellotron sounds, yet it has no tape cartridges or sample ROM. A word of warning here: don’t expect 24-bit, 192kHz glory. The pedal manages to capture the characteristic grit and graininess of the original sounds with a reasonable degree of authenticity, and that’s as it should be. Like the B9, it has a white knob to select from nine presets: Orchestra, Cello, Strings, Flute, Clarinet, Saxophone, Brass, Low Choir, and High Choir.

Mel9 Synth Pedal

Also like the B9 (and all 9 Series stompboxes), it has inputs and outputs in the same configuration, and the first two control knobs balance dry signal and synth output. Mel9’s other two knobs control attack and sustain.

The response from each sound is swift and articulate. The strings and brass in particular benefit from a slight adjustment in the attack time, however. The sustain adds extra time to the sound’s release rather than sustaining infinitely, as a synthesizer ADSR’s could. I preferred playing melodic passages and staccato parts with the sustain dialed all the way back to keep notes from bleeding together; in that case, the sounds will decay and release as long as the strings have energy. 

Mel9’s Strings preset is a beautifully cheesy reproduction of an old analog string ensemble that reminds me of “The Court of the Crimson King,” and the Flutes instantly conjure up “Strawberry Fields.” My favorite of the lot are the cellos, which manage to provide plenty of rosin in the attack, making me again question whether there was any sampling involved. The two choirs are eminently satisfying and sample-like, in a lo-res way. Saxophone doesn’t fare quite as well, with the preset taking on a flute-like timbre above middle C. Don’t expect to play Coltrane, as the attack seems a bit slow for that purpose. Still, it’s useful for filling ensembles and providing pads. Mel9 is great fun to play, and effectively evokes the sounds of bygone days.

Synth9 ($221.30)

Of the three 9 Series instruments reviewed here, Synth9 is the one most closely aligned with the guitar-synth theme. Nine presets are voiced to emulate specific classic analog synthesizers, and they’re titled to hint at their inspirations. As with the others, the white rotary knob selects the preset, while the upper-left knobs set the volume for guitar and synth, leaving two knobs labeled CTRL 1 and CTRL 2 for tweaking selected synth parameters. The function of these two control knobs varies from preset to preset. Control over voicing is limited; rather, EHX has selected what they feel is a representative patch for each preset and developed a modicum of tweaks.

The first selection, OB-X, captures the rich, brassy sound so popular with many Oberheim synths (think, Prince’s “1999”)). For this preset, CTRL 1 tweaks the tone with more high-end sizzle. CTRL 2 does not, as the manual states, select “between 4 octaves.” Instead, it boosts frequencies from low to high in octave increments as you turn the knob clockwise. 

Mini Mood is an expressive lead instrument with two voices, with the second voice offering adjustable portamento. The first control knob sets the second voice’s level, and the second adjusts its portamento time. Turning the first voice down just a bit with the Synth volume knob can get you close enough to Keith Emerson’s gliding “Lucky Man” sound.

String Synth comes reasonably close to the ARP String Ensemble that inspired it, and its programmable filter sweep makes it a ball to play. Likewise, Poly VI uses modulation depth to emphasize a very resonant filter sweep. This last patch provides an unusual and ear-catching lead instrument.

Synth9’s punch and girth get a boost from its built-in compressor/limiter. On some patches, it made the instrument difficult to play quietly or cleanly, as the compression made string releases more audible. (I recommend a volume pedal inserted after the synth’s output.) Switching from bridge to neck pickups can slightly mellow the otherwise brash sound of some presets, but don’t expect any ethereal and silky pad sounds. Synth9 sounds are their own argument for additional controls and control-pedal inputs. A shorter release time would have made some sounds respond better to fingerpicking.

Synth9 is an inspired plug-and-play instrument, but if you are a fan of the instruments that inspired the sounds, you’ll want a more varied palette. Let’s hope that EHX is encouraged to release additional 9 Series pedals.

Next month in Part 2, you’ll read about the Source Audio C4 synth pedal, the Meris Enzo polyphonic synth and effects pedal, and Yonac Roxsyn, a polyphonic guitar synthesizer disguised as an iOS app. Stay tuned.

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