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Guitar Modulation Effects [Producing & Recording Guitar Excerpt]

Modulation is often a point of confusion for a lot of guitarists and producers and engineers. That’s because it’s sometimes a blurry line, because some of these effects can sort of simulate each other, but there are some very clear distinctions between say, a Leslie spinning speaker cabinet and a flanger, versus a chorus, versus a vibrato, right? Versus a tremolo.

They each individually can do their own unique thing, so I’m going to focus this section on what makes each of those effects unique in its own right, and how we can imply a Leslie speaker using a chorus pedal. But don’t get it confused, because even though you can setup a chorus pedal to emulate a bit of Leslie sound, it’s still not quite the same thing.

I’m going to start with the rotating speaker sound. This is most commonly associated with the Leslie speaker cabinet. They were used alongside with Hammond B3 organs, and guitar players, actually most notably The Beatles started doing this in the 60’s, they started running vocals and guitars through them. Basically, it’s a speaker cabinet with a horn and a bass speaker in it, and they spin.

So there’s a tube preamp in it, you send your signal into it, and there’s a crossover, so it separates the low frequencies and the high frequencies. The low frequencies get sent to the low speaker that’s spinning, and the high frequencies get sent to the high speaker that’s spinning.

Well, the fact that there’s two different speakers spinning, it creates a warbling vibrato effect. Let’s listen to a little bit of this emulation, which I think the Hughes and Kettner to my ears is still the most authentic sounding one, short of having a real Leslie cabinet, which is not very practical to carry around. If you have a big enough studio, you can get one. It’s definitely worth having to mic up because it’s such a classic sound.

Let’s listen.


[guitar, emulating Leslie speaker cabinet]

There’s a sound you know. It’s such a Beatle-y kind of sound. There’s often two speeds on Leslie cabinets. I’m going to give you the slow speed now.

[guitar, emulating slow Leslie sound]

You can hear it now, it’s a bit of a chorus sound. That’s not exactly what a chorus pedal does, but the spinning Leslie cabinet in slow speed was I think our first introduction to what was going to be the chorus sound later, which was a very different method for getting that modulated sound. The Beatles also used this effect for playing guitar lines.



Mark Marshall

Mark Marshall

Mark Marshall is a producer, songwriter, session musician and instructor based in NYC. More at

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