Understanding Modulation Pedals
Let’s be honest: deciding what kind of modulation effect to buy can feel impossible. I get it. I’ve been there, too, trying to decide between a rolicking phaser and a mellow univibe. It’s basically Sophie’s Choice, but with guitar pedals. In this article, I want to finally explain the difference between every single type of modulation effect and get this straightened out once and for all.
Honestly, this is as much for my own sanity as anyone else’s. I’ve been meaning to cross this off my “To Do” list for years.
Tremolo
Simply put, modulation means “to move,” so every effect that falls under that description moves the pitch or the sound of your guitar. The very first modulation heard in modern music was tremolo. Tremolo is not always seen as a modulation effect, because it doesn't modulate the pitch; instead, tremolo is modulation of volume. Imagine you're in your car, you're cruising down the road, listening to Def Leppard, and you reach over to the volume knob and turn it up, down, up, down, up, down. You are modulating the volume between a low volume and a high volume, which is exactly what a tremolo does.
The very first tremolo unit ever dropped in 1946: the DeArmond Tremolo Control. It’s actually the first ever standalone effect in history (though not the first pedal; that claim goes to the Maestro Fuzztone FZ-1). Tons of tremolos followed, one of the most iconic being the BOSS TR-2. If you go back and watch the JHS Show episode we based this article on, you’ll hear Nick and I jam with the TR-2, and if so, you’ll instantly recognize this sound-- it’s all over the radio, and tons of artists have used it to build riffs and makes chords move.
Rotating Speaker Effect
The next modulation effect was released around the same time as the DeArmond Tremolo: the rotating speaker effect. The most popular version of his effect comes from the Hammond organ and the rotating Leslie speaker. The rotating Leslie speaker is basically a big wooden cabinet with two speakers. The top speaker is a treble horn speaker, and it rotates, throwing the sound out in a 360 degree form, which is a type of Doppler modulation. Doppler modulation is what happens when you're standing on the street and an ambulance passes. The sound of the siren itself modulates because of distance and movement.
One of my favorite DSP pedals that captures this effect is the Strymon Lex Rotary. It even has speed settings that allow you to go between fast and slow very smoothly, naturally ramping up and down just like a Hammond organ and a Leslie speaker.
Univibe
Our third modulation effect is the univibe. This came to us in 1968. The enclosure on this one is bigger than usual, with an easy-to-use foot controller. You’ve seen it on stage alongside guitarists like Jimi Hendrix and Robin Trower. It's a really beautiful sound. A lot of the players who originally played it used it to replicate the rotary speaker effect, but that’s not actually what it does well. It does something completely unique.
The inventor Fumio Mieda is a brilliant engineer from Japan who designed this for a company called Honey that eventually changed its name to Shin-Ei. Full disclosure: his inspiration for this sound is a little trippy. Mieda wanted to recreate the sound of radio waves bouncing off the atmosphere, kicking them in and out of phase, the way he heard them as a child in Japan. Russian signals would phase across the airwaves and cause a strange "washing" sound. He simply wanted to replicate the effect.
Like I said. Trippy.
More than just a complicated phaser, the univibe is the mother of all modern modulation effects. This effect started it all. The original pedal was called the Univibe Chorus Vibrato, which is a little confusing. It’s not really a chorus. It’s not quite a phaser. It’s something completely different. When you go to vibrato mode, it simply removes any dry clean signal from the mix and you have a true, will-make-you-seasick, back and forth phasing sound.
Phaser
Now, modulation technically started in the forties and peaked in the seventies. It’s been fifty years, but everything we know about modulation really hasn't changed much in that time. After all, if it ain’t broke, don’t fix it, right?
That said, the phaser effect had to come out in the seventies, because it fits the aesthetic of this decade beautifully. The 1970s brought us President Nixon, Saturday Night Fever, the Runaways and Star Wars. In 1974, a company from Rochester, New York called MXR came to the market with the Phase 90, their first product. Now, there were a couple other phasers released before the Phase 90, but at the end of the day, this is the most recognizable phaser ever made.
To explain how a phaser works, feel free to reference the chart shown below.
Basically, you have two waveforms. The top line represents your clean signal. You can see the mountain and the valleys in that waveform that are created when you strum a chord or hit a note on your guitar. Now, phasing creates a 180 degree version of the wave form (represented on the bottom line) which is actually silent, but phasing has an LFO, which is a type of oscillator that's going to move this bottom waveform. Imagine this bottom line, this waveform, is sliding back and forth underneath the clean signal. As it does, it produces the swooshing and whooshing sound we think of with the phaser effect.
Now, if you were paying attention, you know this is similar to what the univibe does. But it’s not exactly the same. The phaser produces a true sine wave that is really smooth. The univibe has a harsher drop-off in the waveform, almost a throbbing/pulsing sound.
There are a ton of great phaser pedals on the market, but one of my favorites is the MXR Phase 95. The Phase 95 is really affordable and includes a lot of the different phase effects MXR has made over the years, including the Phase 45 and the Phase 90.
Flanger
Next up is the effect called Flanger, one of the most popular effects of the seventies. Basically, the flanger effect is created when the same signal is mixed together, and one of the signals is a little bit delayed, usually by about 20 milliseconds. That’s one fiftieth of a second. It's just barely off. The two combined signals feed into each other, which creates a delay line feedback loop which more or less layers the sound. As you adjust things like rate, range or color, it intensifies this sonic modulation. You could think of it as a sonic modulation sandwich with layers of delicious filling-- layers of sound-- in the middle. Some of it's moving. Some of it's still. But it all comes together for one delicious experience.
A great flanger pedal-- one of my all-time favorites --is the Electro-Harmonix Electric Mistress, which they recently reissued in a very affordable version. Purely for the novelty of it, though, I’m also a fan of the Lovetone Flanger With No Name, sometimes called Question Mark or “?”.
Chorus
Now, let’s take a look at the chorus effect. This is most connected with the term modulation, which means that when I say “modulation pedal,” you’re probably picturing a chorus pedal. It was also the sound of the eighties, to the point where we all got a little sick of it. Fortunately, time heals all wounds. The chorus is back, and I couldn’t be happier.
Compared to phaser or especially flanger, the chorus is pretty simple. Basically, you have your clean signal mixed with a modulating signal. The result is pitch modulating. Unlike tremolo, which moves volume, the chorus just moves the pitch of your note ever so slightly, at a speed that you set with a rate and a depth that controls how much of the modulating signal there is in comparison to the clean signal. It's really simple.
The most famous modulation, a true classic, is the BOSS CE-2. Pretty much every chorus pedal that you’ve ever played is some variation on this circuit. The Waza Craft reissue of the 1981 CE-2 is a great option and really affordable compared to some of the vintage units. Honestly, there are literally hundreds of chorus pedals and they're all pretty good.
Vibrato
Let me ask you a question: what happens when you take a chorus and remove the dry signal? If you’re willing to massively oversimplify things-- just for educational purposes --the result is vibrato. Basically, chorus is the combination of the two waveforms, and vibrato is just the modulation. That's pretty much it. A lot of people associate vibrato with the vibrato arm they have on their electric guitar, which does the same thing.
A great option for vibrato chorus is the BOSS VB-2, but I also want to plug one of the underdogs here: the TC Electronic Shaker. It's simple. It's cheap. I think you can buy these used for like 10 bucks? At this point, you could probably snag one for free. And it works beautifully.
Ring Modulation
This last effect is a doozy. It’s also one of my favorites. I’m talking about ring modulation.
Now, I've had ring modulation on my pedalboards on and off for about twenty years. I always find ways to use them. They're really fun. It’s a different style of modulation than you’ll get from a chorus or a flanger, and it originated in the seventies with things like the Electro-Harmonix Frequency Analyzer. Mutron and Way Huge have released some solid versions of this as well, but they’re surprisingly hard to find. In my pedal collection of literally thousands, I only pulled out a handful of ring modulations.
My personal favorite ring modulation, though, has to be the Electro-Harmonix Ring Thing. It’s weird enough to almost defy description. Honestly, it's the crazy uncle of the family. You don't even have to know how it works. You just need to know it's crazy, with layers and layers of madness, warbles, pitches, ringing sounds, goblin-like tones. You can’t beat it.
My biggest advice to you, if you want to understand these effects, is that you really need to play them. You can hear people demo their brains out, but you're never going to experience what modulation does and really feels like unless you play the different effects. They can seem super similar when they’re heard through your phone or computer speakers, but when you play them, they are significantly different. It's really important to know that where pedals are concerned, some things have to be experienced. You have to feel how your guitar responds to it, the way it moves with your amp, the way it moves you.
With that in mind, I’d suggest that you invest in a multi-modulation pedal so you can try as big a range of modulation effects as possible. Two great options here are the Line 6 MM4 and the BOSS MD-200.