What Are Filters and How to Use Them
Filters are tools that increase or reduce the amplitude of a certain group of frequencies (in the case for equalizers) or even cut them out (not completely, but almost). This definition can vary depending on which field we are working on (it’s not the same, for example, in the amplifier circuit world) but this applies especially for music (mostly, electronic music) and sound design.
Every sound consists of a series of harmonics, and the importance of audio filters lies in the shaping of those, especially in subtractive synthesis.
Digital filters can be found either included in the synthesizer hardware or software (almost every synthesizer has filters because it’s one of the bases of sound design) or by loading an equalizer in the mixer of your DAW (almost every equalizer has an option to set up filters).
There are a lot of different filter types. Each of them differs in the way in which they cut out or boost the selected frequencies.
A good example of a filter is your own mouth; when you talk, you just generate a repeated waveform (that’s your voice) that is shaped by your mouth, which filters the harmonics in order to create different sounds. The most obvious example is the pronunciation of the letter m, where almost all harmonics are cut out. This same effect occurs when, for example, you listen to a sound that comes from another room (it sounds “dark” because it doesn’t have high frequencies).
In this article, we’ll be covering some of the filter types that you’ll most likely find in any plugin, along with examples of each of them, and some practical tips for using them in your music production.
But first, let’s explain the most important parameter of every filter: the cut-off frequency.
The cutoff point or frequency determines where the filter will start working (either attenuating or boosting). To be precise, the cutoff is defined as the point where the signal is attenuated by 3 decibels, as you can see in the images below.
For example, if you set the cutoff frequency at 2000 Hz, everything below that will be attenuated or cut if it’s a high-pass filter (which I’ll explain in a minute) and everything above that will be attenuated or cut if it’s a low-pass filter.
Now let’s go ahead and explain the most common filter types, which you’re most likely to find in your synthesizer.