[EDITORS NOTE: This is another post by Guest Writer Rob Gainey. Rob and his publisher, Hal Leonard, have been gracious enough to allow posting of some excerpts of his recent book "Rockin' Your Stage Sound". If you enjoy this, or any, of his articles please consider supporting his efforts by purchasing his book...it just may help Rock Your Stage Sound. - Ray]

Flangers/Choruses/Phasers
These units are all similar in that they mix a processed signal with the original unprocessed signal to produce a particular sweeping or swirling effect. Flangers and choruses both change the speed of a delayed signal to produce a swishy or sloshy sound, depending on their settings. Phasers shift the phase of a signal by using a filter to sweep the frequency range. They all sound different when you hear them one after the other, but they are remarkably similar. Extreme settings on a flanger or chorus will produce a warbling effect known as vibrato. While phasers have Speed and Depth controls, flangers and choruses can also have Sweep in their settings.
An ordinary delay unit can be used to produce a flange or chorus effect if it has a modulation control, which automatically varies the speed of the delay. Sweep is the equivalent of delay time, Speed is the equivalent of modulation, and Depth is the equivalent of the feedback or repeat control of a delay unit. With no modulation and longer delay times of 40-60 ms, this is called a doubler, because it sounds like two people playing the same thing ever so slightly out of time.

Delay
Delay is an effect in which you can hear the individual repeats of a signal. Often called “echo,” this is one of the most popular effects in the history of audio. There are many types of delay units, from old tube Echoplexes to pristine-sounding digital delays, but they all perform a similar function: to repeat a given length of your input signal at least once, often more. With each succession or repeat, the volume decreases; at least for normal delay usage. Most delay units have a control for length, another for feedback (the number of repeats), and a mix control that allows you to balance the delayed signal with the original signal. Delay is best used before any reverb, as this is what occurs in the real world and sounds most natural to us.

Reverb
Often confused with delay, a reverb unit produces a large number of “reflections” by means of a digital algorithm. No discrete “echoes” can be heard; instead it sounds like you’re playing in a cave. The evolution of the reverb effect went from using a microphone and speaker in a tiled room to a long box with a “plate” in it or a small box with “springs” to the now famous digital reverbs with complex space modeling, backward reverbs, and “gated reverbs” that build and end abruptly.
The operation of these units will vary considerably, but there are three main parameters on most digital reverbs: Room, Density, and Decay. Smaller rooms produce shorter, tighter reverbs, Plates produce medium-length reverbs, and Halls produce longer reverbs. Each program uses a different algorithm to produce a particular tone for each reverb. Density controls the amount of reflections produced by each program. Decay determines how long the total reverb time is from the initial sound until the final reflection has decayed. While there are often a few more parameters, each unit has a different set of features, sometimes even for different programs.
Reverbs should always be last in the chain, as they usually sound most natural after everything else. The tails they create would sound quite unusual before other units like harmonizers, choruses, and delays, but if you’re out to discover that “unique tone,” this may be the one rule you’d want to break, and my leading choice for a strange effect.

Line Drivers
A line driver really isn’t an “effect”; it simply amplifies a signal that has been weakened by multiple effects units in series to a level that will drive a long cord to an amp without a significant loss of gain. This unit will rarely be switched in or out of the signal path; it is usually left in the whole time. It doesn’t provide “distortion” as we know it—its main purpose is to cleanly amplify a signal without changing the quality, just the level.
These units are best used very last in your signal chain, even after any reverb. If you only have a few effects, you may not need one at all. If you have six or seven units, you may need one. It really depends on how much gain your amp has. If you have plenty of gain left over after all is said and done, you don’t need one. If your gain is cranked all the way up and you could use some more level, then you definitely need one.
An entire library could be devoted to just effects, but that’s just not practical for the purposes of this book. There are quite a few other effects—some of them one-of-a-kind specialty units that nothing else can replicate, but in the end, they will typically fall into one of the four categories we have discussed here. As long as they are sequenced correctly, you should be able to make what you have work with few problems. Just keep in mind that people come to hear music, not effects.