The marriage of synthesizer and guitar is a decades-old relationship. And it’s been marked by a few blockbuster hits and some spectacular misses. Influential synth builder ARP created the Avatar in 1977, which required a special hex pickup and used pitch-to-voltage technology. So few were actually sold that the company, which had previously produced such massively influential synths as the 2600 and the Odyssey, nearly tanked.

Roland attempted the synth effect in the same year as ARP with their GR-500. But though both companies faced similar challenges, Roland experienced much greater success—most notably the analog GR-700 in 1984 and the later digital GR-33. The GR-33 was a floor-based synth unit with the synth brain from their acclaimed JV-1080 keyboard line and the company’s special GK-2A pickup. The result was a wealth of synth presets that widened guitarist’s palates like few processors before it.

Many guitar synth pedals today do not require a special pickup. Instead they use pitch tracking to detect the pitch of your input signal and use that information to tune and activate an internal oscillator. In other words, the synth tone comes directly from an actual synthesizer circuit, not a modified version of your guitar signal. It’s a much simpler approach that streamlines hardware, simplifies the interface, and can transport your guitar to new dimensions of tone possibilities.

Where You’ve Heard It
You certainly can’t talk about guitar synthesizers without mentioning prog-rocker and studio extraordinaire Adrian Belew. Though his primary project is King Crimson, his unorthodox virtuosity has been a highlight of records by art-rock acts including Frank Zappa, David Bowie, Talking Heads, and Nine Inch Nails. On the King Crimson track “The Sheltering Sky” you can hear his synthesized lead work, which, like so much of his work, blurs the line between guitar and synthesizer.

Another more recent prog-rocker who utilizes guitar synthesis as a regular feature of his playing is Omar Rodriquez-Lopez of The Mars Volta. On their fantastic De-Loused In The Comatorium album you can hear Rodriguez-Lopez’ infectious and energetic hard-rock playing style paired with long, avant garde-influenced noise sections which, like Belew, blur the guitar/synth divide. In the track “Cicatriz E.S.P.,” filtered synth guitars subtly punctuate the transitions between brilliantly crafted song structures.

How to Use It
The first step to tapping into a guitar synth pedal is setting the input sensitivity so that the pedal has enough signal to detect the pitch and intensity of your playing. Typically there will be a dedicated control for this. It is often beneficial to roll your guitar’s tone knob to zero and use the bridge pickup. This will eliminate excessive harmonic content that can confuse the pitch tracking mechanism. From this point you can start sculpting your synth tone.

A basic synth lead is one of the simplest tones and easy to dial in quickly. Simply select an oscillator, disengage any filters, and let if fly.

Synth octave up at 50%, synth interval 5th down at 50%, dry at 0%

The resulting sound has a bright, quick attack—like a guitar, but you can sustain steadily as long as the unit detects your input signal, like a keyboard. Many synth pedals also have harmonizing capabilities, which further contributes to a classic, emotive lead sound.

For a synth bass tone, take the simple lead line described above, lower the pitch of the synth down one octave, and add a filter.

Octave blend at 50/50, filter cutoff at 3 'clock, resonance at 2 o'clock

The lower octave fattens up the sound and the filter can be set to add a percussive element by setting it for a fast-but-not-too-fast attack and short sustain (or decay, depending on the unit). The filter will open quickly as it detects a note creating a percussive sweep on the attack to roughly mimic the spank of a slap bass. A short sustain will whip the filter back after the attack, again contributing to a percussive synth sound. The proper speed of the filter settings depends on the speed of your riff, so plunk away and adjust accordingly.

Creating a lush pad is a bit more work and may require some additional processing such as chorus, reverb, and delay, but the results can be stunning.

Detuned octave down blended 50/50, triangle VCO, glide on, glide at 9 o'clock

The basic idea is that you want a darker tone, a slower attack, and a harmonically rich mix of oscillators. For a darker tone, set the filter cutoff much lower so that high frequencies are suppressed. Set the filter so that the attack sweeps are very slow, like an orchestral swell. Then add some harmonic content like a major or minor 3rd, depending on your composition. More harmonic content will help you to achieve a lush, rich sounding synth pad.

Wave - Depending on the unit, there may be numerous voltage controlled oscillator (VCO) wave options. Some of the more common VCO types include Sine, Triangle, Sawtooth, Ramp, and Square. Sine is the simplest waveform and produces the purest tone, generally free of harmonic overtones and perfect for pads. Triangle sounds like a brighter Sine wave. Sawtooth and Ramp are inverted versions of the same waveform and have a bit more upper harmonic content that translates to a buzzing tone, rich in high frequencies, and perfect for cutting leads. Square waves have a big bold melodic voice that is great for driving melodic lines, but also have a fair amount of high frequency content. Pure square wave evoke a vintage video game tone to most that can sound dated to some ears, but is perfect for funky and unmistakably synthy sounds when you need them.

Filter – Because a single VCO can only produce a single waveform, its frequency spectrum will remain steady without any shifts in tone characteristics (imagine the sound of a flat-line heart monitor). This is why most synth pedals run the oscillators through a voltage-controlled filter (VCF). The filter allows you to change the frequency spectrum of an oscillator over time, producing a more natural note response. The classic filter has four basic controls—Attack, Decay, Sustain, Release. These controls determine how fast or slow the filter responds to a note. A quick attack will open the filter immediately producing a bright blast, like a brass instrument. A slow attack will produce a long swell from dark to bright, like a rising orchestra.

Envelope - Another common element of synthesizers is the envelope. Think of the envelope like a VCF that reacts to the loudness of an oscillator rather than frequency. In synth pedals that are made for guitar, envelope controls are less common because the unit uses your playing dynamics to directly control the envelope, which makes perfect sense for guitarists and makes the guitar a uniquely expressive interface for a synth.

Pedals We Tested
In terms of ease for achieving basic synth tones, Subdecay’s Octasynth and Electro-Harmonix’s Micro Synthesizer are great for beginners looking to get their synth on. We also tested some wilder options for more adventurous players.

Snazzy FX Mini-Ark - When it comes to an analog guitar synth you can’t get much more pure and straightforward than the Mini-Ark. Not only does it use playing dynamics and pitch to control an internal analog VCO synthesizer, it also features control voltage (CV) connectivity, making it as much a guitar/modular synth interface as it is a standalone synth pedal.

The Mini-Ark’s interval VCO is a square wave oscillator that has a distinct video-gamey type of sound that is full of high and low frequency content, making it great for cutting through a mix. In addition to the root note oscillator you have a multi-position Octave selector and a multi-position Interval selector each with associated level controls. There is an array of preset intervals that can be selected including thirds, fourths, fifths, and octaves. A Clean/Dirty switch adds a slight bit of overdrive grit to the signal.

With the Sustain/Gate switch in Gate position the synth signal will stop when the pedal stops detecting a signal. With the switch in Sustain position, the synth signal will continue to oscillate until the pedal detects a new note. This is great for creating impossibly long sustaining notes. The multi-position Magical Selector is, not surprisingly, the most interesting control on the Mini-Ark. The first position is the straightforward synth pitch-shifting mode. The other settings modulate the oscillators in ways that vary from slight vibrato to unpredictable bends with crazy bursts of noise.

The Mini-Ark sounds thick and beautiful, is extremely simple to use, and has some unusual capabilities that will keep things interesting. And guitarists who work with modular synths are going to dig this unit for its ability to interface with other CV capable gear.

Pigtronix Mothership - Like the Mini-Ark, the Pigtronix Mothership is a monophonic analog guitar synthesizer—it reads a single incoming note and responds with a variety of synth tones. Pigtronix is one of those pedal makers that loves to give you control of every aspect of the effect. And for some players, just the sight of one of these beautifully comprehensive units can boggle the mind. For others, the sheer volume of controls and features adds substantial value and room to grow and learn. That’s exactly what you get with the Mothership. With ten knobs, six switches, and five in/out jacks, the Mohership might seem perplexing at first glance. But the features make perfect sense with practice in practical applications. One advantage to the Mothership is that you can select between square wave and triangle wave oscillation. The triangle waveform has a much smoother, less abrasive, and less distinctive sound than the square wave, which is great for creating softer synth sounds. The Mothership has a glide control for portamento effects. You can also plug in an expression pedal to control the Mothership’s whammy setting and the pedal has a ring modulation circuit. It all adds up to a ridiculous amount of sonic possibilities.

Electro-Harmonix Pog 2 and Electro-Harmonix HOG - These two well-known effects from EHX could conceivably be discussed in either the synth or pitch shifter category, but because you can range from simple pitch shifting to thick organ-like walls of sound they’re very synthy in terms of capabilities.

The second incarnation of the Polyphonic Octave Generator (Pog 2) is the latest version of EHX’s legendary Pog from 2005. This unit reads your signal and produces numerous octave signals that can be blended independently using sliders. This sort of design takes its cue from the stop controls on pipe organs where you adjust sliders to control the amount of air sent to the various pipes on the organ. The Pog 2 allows you to independently control the levels of octaves from two octaves up to two octaves down. You’re also able to control the attack of the octaves, detune higher octaves, and process the overall sound of the unit with a completely adjustable low pass resonant filter. The Pog 2 also enables presets to be saved for performance. That’s a lot of control and a ton of performance parameters. But the slider interface makes tweaking absolutely intuitive. Without the filter the Pog 2 produces a wide variety of convincing organ sounds, and can also be used subtly to thicken up your tone. You can use the Pog 2 in the same way you would use any standard octave pedal too. Using the filter gives you the ability to produce some more unique synthetic sounds and wah-wah-like tones.

The Harmonic Octave Generator (HOG) builds on the basic idea behind the Pog but includes even more controls that allow you to shape your tone even further. To start, the HOG gives you four octaves up, as well as three additional fifth interval sliders to add a bit more harmonic richness to your tone, creating an even more brilliant and convincing organ tone. The HOG also allows you to adjust the envelope of the lower pitch shifted signals separately from the envelope on the higher pitch shifted signals. For instance, you can have the beefier low octaves start immediately while shimmering higher octaves and fifths fade in slowly. The results are unique to the HOG—you can’t find these types of tones in any other unit.

The HOG gives you expression pedal control over the octaves and/or filter if you opt for it, as well as MIDI connectivity and an optional performance footswitch used for storing and recalling presets. And there are several functional modes that enable bends, filter modulation, and freezing. You may have heard of the recent Freeze pedal from Electro-Harmonix. The functionality of that unit was pulled directly from the HOG’s Freeze-Gliss setting. The basic idea behind the Freeze-Gliss setting is that you can capture a moment in sound and let it sustain indefinitely while you play over the top. Fans of this mode liked it so much that EHX gave it its own pedal. The possibilities are nearly endless with the HOG but, like the Pog 2, the intuitive slider interface eliminates confusion.

Dwarfcraft Devices Satan Oscillate My Metallic Sonatas (SOMMS) - Dwarfcraft is probably best known for their utterly destructive fuzz pedals, but they also have a handful of completely oddball units that defy categorization. The SOMMS is just one such unit, and its capable of creating walls of harmonically twisted synth tones that you can blend with your dry guitar signal. The SOMMS has an input and an output, though it does not modify your guitar signal in any way, nor are the oscillators within the unit controlled by the guitar signal. A blend control determines the balance of dry guitar versus internal synth in the output.

The SOMMS has four independent square wave oscillators with controls to set the tuning and the level of each. The most interesting control is an ultra-cool joystick that is large and rugged enough to be controlled with your foot. The SOMMS is most effective at creating a huge wall of unholy synth droning as a backdrop to your guitar signal.