For guitarists who dig the electronic sound of a synthesizer, guitar synth pedals can combine the best of both worlds—the psychedelic glow, glitchiness, and fat tones of a synth’s oscillators with the expressiveness of guitar strings. There are a handful of such devices on the market that use a guitar signal to drive synth oscillators inside a pedal. And depending on the implementation, the results can range from swooping UFOs, to buzzing leads, to chugging synth bass.

Synth pedal controls and parameters can differ wildly and prioritize different aspects of synthesis. Red Witch’s Synthotron, which is a synthesizer, sample and hold, and envelope filter, takes an ambitious but streamlined approach by packing a lot of sound-sculpting features into a box that can be a handful at times, yet yield spectacular results.

Expansive Synth Controls
Outwardly, the Synthotron is a delicious fusion of ’70s graphical concepts (there’s more than a few hints of Mu-Tron design in the multi-colored enclosure) and Red Witch’s forward-thinking design notions. The pedal is built around a synth engine divided into three sections—octave up, octave down, and tremolo—as well as a filter section. Each section is assigned its own colored block, which helps orient you on the fly. The left footswitch engages the filter and its controls located on the right side of the pedal (which is a tad counterintuitive), while the right footswitch engages the synth section. And being able to run either side independently or in combination really opens up the sonic possibilities of the Synthotron.

On the Synth Side
The Synthotron is a 2-channel synth pedal, which means that the tracked pitch from your guitar controls the pitch of two separate square-wave oscillators. Square waves are a common choice in synth pedals because they sound buzzy—not unlike a distorted guitar—but also have a very evocative video game-like sound, which can be heavy, funky, or hilarious depending on how you use it. The Synthotron’s square-wave tone, however, is a fat, rich foundation for tweaking.

The first channel can be set to one or two octaves up, and the second channel can be set to one or two octaves down. Each octave channel has a dry level knob, which controls the balance of effected and clean signal, and a decay knob that dictates the sustain of the synth signal. The last effect on the synth side is a tremolo channel that, like the octave-up and octave-down channels, can be bypassed via a mini-toggle.

The filter section controls an envelope filter that produces an auto wah-like effect and the range control determines whether the sweep occurs across higher or lower frequencies.

There’s also a sample-and-hold switch, which overrides the envelope. This moves the filter position around in an unpredictable, floating fashion. There’s also a control that sets the speed of the sample-and-hold generator. Faster settings produce the sound of a robot in deep thought. Slower settings bring to mind the drifting, psychoactive states.

Gateway to Gonzo
One of the most important qualities of any pitch tracking effect is its ability to accurately register the pitch of your instrument’s signal. Some players want 100-percent perfect pitch tracking. Other players prefer the quirky, less-stable pitch tracking common with vintage analog synths. The Synthotron’s tracking injects just enough of that vintage quirkiness while remaining musical. The pedal also has an internal trim pot that allows you to adjust the pitch tracking sensitivity.

Because the synth tones are generated by the pedal itself, pickup selection on your instrument will not impact the actual synth sound. Pickup selection does produce slight variation in pitch tracking though, though my Strat’s single-coils tracked with ease, and my Gibson SG’s meatier humbuckers tracked more reliably than single coils. In any case, the Synthotron’s wet/dry control allows you to create an effect that blends in a subtle amount of square-wave buzz. Independent level controls for each of the two oscillators allow you to mix low and high octaves like you would with any flexible octave pedal.

The Verdict
The Synthotron packs a lot of analog synth power into a small package. Given its small size, the pedal’s ability to perform dual-voice analog synthesis, tremolo, filtering, and sample-and-hold is impressive. The independent mixing controls give the player the ability to strap on their chef ’s hat and adjust signals to taste. Analog-synth fans will appreciate the pure analog circuitry of both the pitch tracking circuits as well as the oscillators.

And when you’re looking to step away from the synth, the Synthotron’s filtering channel can be used independently for funky, envelope-filtering effects. All these tone permutations, plus each effect’s ability to go from tame to unhinged, makes the Synthotron not just powerful, but practical and musical as well.