Someone Please Explain Modulation & Compression Effects To Me???

Discussion in 'The Stomp Box' started by tonytrout, Mar 14, 2019 at 4:40 PM.

  1. tonytrout

    tonytrout Friend of Leo's

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    Hey, fellas & ladies!!!!

    I should know this but.....can someone be so kind as to explain (in language I can understand) what "modulation" & "compression" effects do??

    Thanks!

    I should know all of this stuff since I've played guitar for over thirty years but....I don't know half the stuff I should know...LOL!!!
     
  2. mexicanyella

    mexicanyella Tele-Holic

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    I'll take a stab at it:

    Modulation effects (delay, chorus, flanging, phase shifting) incorporate some form of delaying the guitar signal (in other words, "storing" it momentarily and playing it back either as echo-sounding delay repeats, or along with the undelayed signal in varying time intervals and amounts to cause chorusy shimmer (numerous Police songs, Crowded House's "Don't Dream it's Over") or jet-engine swooshy flange effects (Van Halen's "And the Cradle Will Rock") or chewy-sounding phase shifting (Bowie, "Golden Years"). By combining a slightly delayed signal with an undelayed one, you get phase cancellation of various frequencies in the signal. Shifting the delay interval around causes shifting phase cancellation.

    Compression effects basically reduce the initial spike of volume when a note sounds, then "turn it up" as the note decays, making it feel fatter and sustainier. There's usually some sort of adjustable makeup gain control which allows you to boost the output signal to compensate for the amount you reduce that initial volume spike, or even to give an overall boost over and above whatever the initial signal was. Some of the appeal of cranking a tube amp comes from the natural compression process that occurs when you ask a tube amp to deliver at levels near its operating limits. You can also get some compression effects when you push speakers past a certain point, as you start to lose some of the efficiency of converting the signal into sound through running into the speaker's mechanical limitations, or you start to lose some of the signal to heat in the voice coil and magnet assembly. Using a compressor with guitar or bass can give you some of that cranked-amp feel at lower volumes when set conservatively. Set to extremes, it can give a really sustainy, squishy-feeling response, which can be cool or weird depending on the context.

    Related to compression is limiting, which just limits incoming volume spikes from passing a certain amplitude, or loudness, threshhold. That's found more often with bass amps, or PA equipment, where you are trying NOT to overdrive the power amp or speakers because you want higher fidelity than you usually do with guitar.
     
  3. Lawdawg

    Lawdawg Tele-Meister

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    I'll do my best!

    "Modulation" effects typically refer to effects that "modulate" or alter the guitar tone at a set rate/tempo. The most common examples are tremolo, flanger, chorus, phaser, and vibrato.

    Tremolo is easiest to explain and start with -- the effect "modulates" the tone by increasing and decreasing the guitar volume at a set rate of speed.

    Vibrato does the same thing except it modulates the pitch of the guitar tone instead of the volume.

    Flange/Chorus are a little more complicated. Both of these effects use a short delay time to create a filtering effect. What is technically being modulated is the delay time which creates the classic whooshing sound of the flange or chorus effect.

    Phaser is a little more complicated still. In this case, the whooshing effect (think EVH's tone in "Eruption") is created by combining the original guitar signal with the same signal that's been put through an all pass filter which then has its phase modulated. When you combine two identical signals with an altered phase like this it creates a filtering type of effect.

    All of these are easier to demonstrate than explain but that's a basic explanation. There are other more esoteric modulation effects, like ring modulation for example, but these are the most common ones.

    Compression is an effect that reduces the increase in volume of a guitar signal after a certain threshold is crossed. The practical effect is to even out the guitar volume which can be good or bad depending on what you're trying to do. Think of it this way, you play a guitar softly the volume is low, you play medium the volume is medium, you play it super hard and the volume is as loud as the guitar can go. Now you insert a compressor with a medium threshold. Now when you play softly the volume is low, when you play medium the volume is medium, but now when you play loud the volume is just a little bit more than medium. There's a bit more to it than that, but that's the very basic concept.

    Not sure if any of this helped, effects are usually easier to demonstrate than describe. Hopefully there are other folks here who can do a better job!
     
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  4. logans_tele

    logans_tele Tele-Meister

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    Modulation effects are wooshes, swooshes, wah-wah-wah, swirly sounds. Compression is making your softest picking and loudest picking closer to the same volume. Either one can be very subtle and almost not noticeable, but they can also be very dramatic depending on exact settings.

    Gross oversimplification, I know. But really, your ears are the best teachers here. Go watch a youtube demo of a Strymon Mobius pedal and you will then understand what modulation effects are.

    Watch youtube demos of a few compression pedals and you'll get the idea there too.
     
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  5. Art VanDelay

    Art VanDelay Tele-Holic

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    Modulation is always time-based and repeating. Tremolo is the simplest because you speed it up or down (frequency of repeats), and then determine the depth (high & low of signal wave).

    Compression reduces volume spikes and amplifies lower powered dynamics. It's the second part that stumps people because any microphonics you might have will be brutally amplified. I think of compression as taking a mathematical average of your signal's highs and lows in volume.
     
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  6. Guitarteach

    Guitarteach Poster Extraordinaire

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    Modulation... swirly, throbbing, whooshing stuff

    CoMPReSsION >>> compression.... squashes/flattens the loud bits so they don’t jump out and everything is more even
     
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  7. E5RSY

    E5RSY Poster Extraordinaire

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  8. telepraise

    telepraise Tele-Meister

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    Mexicanyella covered them about as succinctly as anyone could. I think genre plays a big part of what's useful and what isn't. Compression is used pretty heavily in hot country hybrid picking and chicken picking, really helps you just hammer through the runs with less pick action. Listen closely to what Brad Paisley does and you can hear it at work. Dang, Wampler has even made some pedals that he had a hand in designing.

    Modulation can flesh out your tone on slower numbers (I prefer chorus modestly applied) and add some shimmer to your sound when carefully applied. When overdone, it can start to sound like the 80s all over again.
     
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  9. Art VanDelay

    Art VanDelay Tele-Holic

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    Did someone say 80's?????

     
  10. mexicanyella

    mexicanyella Tele-Holic

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    Oh, I've got some 80s chorusy modulation meltdown for you:

    pretty much all the guitar in this, but especially the outro figure, beginning at 4:08

     
  11. codamedia

    codamedia Friend of Leo's

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    Modulation is not (in itself) an effect. It is just a blanket term that encompasses Phase, Flange, Chorus, Vibrato and all of it's variants.
     
  12. 65 Champ Amp

    65 Champ Amp Tele-Holic

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    Modulation, is relatively easy to grasp. Modulation is what happens when two or more vocalists try to sing in unison. The slight variations between voices can create depth, fullness, atmosphere, dimensionality, etc. Most modulation effects are achieved by ... modulating one of those voices in some way and mixing it back in with an unmodulated voice.


    Compression, on the other hand, is complex and mysterious. And anyone who actually does understand it had to sign a binding document in bodily fluids not to share the secret.

    There are two kinds of guitarists ~ those who do not have a single clue what compression is, how it works, or how to set the parameters, but pop into every compression thread to say that compression ruins their dynamics.

    The other kind of guitarists are those who do not have a single clue what compression is, how it works, and how to set the parameters and pop into every compression thread to say it does “something” for their sound, and they miss it when it’s off. (I am more in this camp)

    The single most important thing to know about comp is that compression is how the television stations are able to make commercials seem incredibly loud and in your face without actually turning up the volume.
     
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