As one of the oldest electric guitar effects, tremolo has spiced up records in every style for decades. The mysterious vibe that tremolo can lend to music is beyond question. And unlike a lot of complex effects, it’s dead simple: The throbbing sound is simply volume attenuation—the equivalent of having a little monster rhythmically turning your amp down and back up again several times a second.

Z.Vex has built its reputation on twisting the familiar, however. So it’s no wonder that they’ve found a way to turn the humble tremolo circuit inside out with the Sonar, a square-wave tremolo designed by Z.Vex engineer and Instant Lo-Fi Junky designer Joel Korte that seeks to extend the boundaries of this timeless effect.

The Rhythm of the Waves
One of the Sonar’s primary objectives is to play nicely with distorted amps and pedals. It achieves this effect by incorporating a very tight gate between each tremolo pulse, which cuts the entire signal with incredible precision that kills any sort of squealing feedback or signal blur when the effect ramps down.

Four knobs control the effect’s parameters—volume, speed, pulse duration (aka “duty”), and “delta.” The latter is the key to one of the pedal’s coolest features. Depending on how you set the switch, it gives you the ability to ramp up to blindingly fast speeds or down to throbbing, tortoise-slow tempos. Hitting the tap switch twice sets tremolo speed on the fly, and a mini switch determines whether the pedal doubles or quadruples the tapped tempo. The pedal also gives you some of the capabilities of the rather grotesque Machine—Z.Vex’s chaotic crossover distortion pedal. These capabilities push the effect beyond conventional tremolo and deliver some really strange and abstract sounds.

The addition of the Machine circuit doesn’t make the Sonar a tool exclusively for noise-makers with extreme sonic ambitions. Z.Vex also threw in an array of hidden controls for attack, release, and depth, which can be tweaked from the speed, duty, and delta knobs while holding down the tap switch. Playing around with these can help you shape the Sonar into a more conservative tremolo that will evoke the classic sounds of vintage Fender amps.

Sending out an S.O.S.
When it comes to heavy tremolo, the Sonar performs exactly as advertised—meticulously cutting the signal with the force and precision of a master sushi chef. With a Mesa/Boogie Multi-watt Dual Rectifier cranked full bore, the pedal refused to allow any feedback or signal to pass between pulses. It’s even more effective when the Sonar is placed in the amp’s effects loop—providing a deeper, more percussive edge to the sound and completely cutting even the faintest traces of background wash.

The pedal’s amazing speed range is remarkable too. You can set the pedal to speeds so fast that the effect becomes almost undetectable. Slower settings lend themselves well to rhythmic chord progressions. If you really want to throw the audience for a loop, the switchable ramp, or delta function works amazingly well for dropping the speed to a pulsating, mechanical throb, or speeding it up to rapid oscillations that sound like a robotic heart attack. The effect can be wildly theatrical too. For example, you can begin by playing a serene melody and then ramp it up to near self-implosion at the end. This is one of the wildest sounds I’ve ever heard come from a Z.Vex pedal.

Throwing the Machine circuit’s blistering distortion in to the mix saturated the highs and mid with a classic Ministry-infused industrial rock edge and highlighted the tremolo’s focus. It’s also pretty amazing what textures the Sonar can apply to a single note. By adjusting the speed on the fly, you can make it sound like your tone is being splattered against a wall.

The Verdict
The Sonar’s capabilities stretch well beyond mere humdrum tremolo. Enabled by the ingeniously applied gate, the pedal’s lacerating pulse makes it an exceptional tool for molding familiar, but truly tweaked tremolo sounds. But it’s also versatile enough to produce tremolo tones that border on classic or maniacal depending on how you employ the Machine circuit. In true Z.Vex style, the Sonar stretches the boundaries of what we can expect from a great tremolo.