Audio filters were always playing a huge role as indispensable tools in music production. They are used for a variety of purposes, from audio cleanup to special effects. Filter parameters can be copied, pasted, automated, and adjusted in real-time. In addition, audio filters can help to remove distracting frequencies, reduce loud sounds, and add ambiance to a sonic space. Generally, filters are much better at removing components of a mix than they are at adding something that wasn’t in the original recording.


World of filters


An audio filter is a frequency-dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. To put it simply, they can amplify (“boost”), pass or attenuate (“cut”) some frequency ranges. To name a few that are most used we could mention low-pass, hi-pass, band-pass and all-pass types of filters. These days it seems that we have many new and exciting types of filters that are available in different hardware and software synthesizers. In this tutorial, I will show you how to use one of them in a creative way.


Discover comb filtering


A comb filter is actually a type of a filter whose response curve contains a series of notches in a repetitive pattern. If such a filter is varied over time so that the notches move up and down in the frequency spectrum as a group, an effect known as flanging or phasing results. Comb filters are basic building blocks for digital audio effects. Essentially, comb filters are produced when a signal is time delayed and added back to itself. Some frequencies will cancel and others will be reinforced, which can dramatically change the tonal color of the sound. It got its name from looking like a comb when plotted on a frequency response graph.


Let’s spice things up


I have made a simple pluck sound and wrote a midi sequence in a newly created project within SoundBridge. What is more, the midi sequence is gradually multiplying in order to create kind of a rising movement. Unaffected, it sounds like this.


~Pluck sound Multiplying Sequence / Unaffected


This is a fairly clean and simple sound. Let’s spice it up with comb filter automation. For this purpose, I will add a Serum Fx plugin by Xfer which contains a variety of effects. One of these effects is a versatile filter with lots of different filter types. Before adding a filter I will add a Reverb effect, huge in size, which is needed to make a comb filter effect more obvious. In addition, this will introduce more space to clean and mono sound. This is how it sounds with the reverb.




~Pluck sound with Reverb Effect


After that, I will place a filter effect under the reverb in Serum Fx rack and from the filter type menu, I will select a comb filter, named cmb+. In the filter section, I will first set the mix parameter to the maximum. Then, I will move the cutoff parameter all the way to the left and increase resonance and drive to a certain amount. This is because I will only automate the cutoff. So let’s make a new automation line in SoundBridge and start automation of the cut off from zero to let’s say 50 %.




~Pluck sound with Reverb and Comb Filter effect


Finally, as you can hear for yourself, it’s pretty easy to make simple-sounding pluck sound into something totally different.


Download the patch here.