Like auto mechanics, carpenters, and writers, musicians often become skilled practitioners without the benefit of any formal training. So many of us have gotten really good at some section of the business by hanging around studios, sitting in on rehearsals, and watching what great players do onstage. There are producers and engineers who have created world-class recordings without ever attending a recording class.
Hands-on learning is great for musicians, but undertaking the study of music with no particular plan or curriculum also has its disadvantages. In the studio, it really helps to have some technical understanding of what different effects and equipment actually do. We all have a general idea of how a flanger sounds, for instance. But what is it? How is the sound produced? Having more clarity about these details will give us a greater command of the studio and the sound of our music in general. Without further delay (or echo), let’s dig into the details of some of the most common production effects.
Reverberation is the persistence of sound after a sound ends. In any acoustic space, you can imagine the many reflections of a sound moving in all directions, being absorbed (or partially absorbed) by the surfaces they encounter, and being reflected back into the room as they bounce around. To distinguish reverb from other sound-persistence effects like echo, reverberation is defined as a sound reflection lasting less than 50 milliseconds after the sound ends. That’s five percent of a second, which is a pretty short time in most applications, but as we all know, it’s a long time in music.
The reverberation time is the amount of time it takes a signal to drop by 60 decibels. The ability of a surface to absorb a sound is the absorption coefficient, measured from 0 to 1. In this equation, 1 would be an open window, allowing all sound to pass through, while a hard concrete wall would be close to 0, reflecting almost all signal back into the room.
When viewed from this perspective, it’s easy to see that reverb is a very complex phenomenon, with each room having its own unique sound and character. We have several effective ways to replicate this effect, such as capturing and reflecting sound using a coiled spring (as in a guitar amplifier), a metal plate, or an echo chamber with a microphone inside. Mostly, we use digital architecture these days. But of course, microphones in a large room produce a distinctive natural reverb that would be almost impossible to duplicate in a digital box.
How is echo different from reverb? Technically speaking, an echo is a reflection from a single source, and it can take longer than 50 milliseconds to arrive. Unlike reverberation, natural echoes are difficult to achieve in the studio…unless your studio includes a large concert hall. That’s because the ear can’t discern an echo from the original sound unless it’s delayed by more than 1/15 of a second. Since sound waves move fast (about 343 meters per second), the reflecting surface would need to be 17.2 meters from the listener to produce an echo. That’s probably farther than the farthest wall in your studio.
Luckily, digital effects are here for us. The original Echoplex, first used in the 1950s, simply recorded the sound source on analog tape, playing it back with some delay. Guitarists loved it, and it became a staple of pro studios for vocal applications, too. If you find one at a tag sale, snap it up: originals are worth at least $900 these days, which would have bought you a whole studio in 1950.
By the way, contrary to the urban myth, a duck’s quack does echo. It’s just such a short, quickly-decaying sound that the echoes are weak and hard to detect. These days, an echo is frequently referred to as a delay.
Flanger effects can have applications for almost any instrument or vocal in the right context. We can all picture what a flanger sounds like, but why does it sound that way? How is the signal generated? Well, it’s actually a form of delay. A flanger combines two identical tracks, one of which is played back less than 20 milliseconds later.
The bonus effect that creates that flanger sound? The amount of delay on the second track changes cyclically. In other words, the period of the delay keeps getting longer and shorter. This period is very short, but the rotation of the delay creates peaks and valleys in the signal in which some frequencies are temporarily reinforced while others are not (what’s known as comb filtering).
Isn’t that the same thing as a phaser?
Almost. A phaser also mixes a "wet" sound with a dry one, but the flanger produces peaks and valleys in a harmonic series, while the phaser produces them without a series, resulting in a more random effect. Phasing on vocals creates a robot effect, because only certain frequencies are reinforced. This simulates machines, which generally produce only certain frequencies, while living things produce a full range of frequencies.
This might be the weirdest effect out there. It’s called a ring modulator because the tone was first achieved by a ring of diodes inside the effects box. Once again, we’re merging two signals: the signal you’re playing and another one that’s generated by an internal oscillator. Then the two signals are multiplied, resulting in new tones at the sum and the difference of the two initial frequencies. These tones have no harmonic relationship to the original notes – it’s just math!
To tame this random, unmusical sound, some amount of the original tone is passed through the processor, so your original note is still audible…but accompanied by wacky noise.
Tremolo and volume
You probably already know that a wah-wah pedal is just a tone control with a foot pedal attached to it. Well, a volume pedal is just a volume knob for your foot, and a tremolo is just a volume oscillator. In a cycle, the tremolo effect takes the amplitude of your input almost all the way to zero, then back to 100 percent. You can alter the speed of the effect. That’s it! But like the wah-wah, this simple effect can be profoundly effective, giving you yet another tool to make amazing music.
Jesse Sterling Harrison is an author, recording artist, and part-time farmer. He lives in Massachusetts with his wife, three daughters, and a herd of ducks.