Introduction to Filters

Following on from last week's blog on Filters, this week we'll delve into the fascinating world of filters.

These useful devices allow you to mould the sounds you generate from your oscillators or with samplers into entirely new entities - changing a harsh lead into a warm pad, a deep bass into a piercing effect... they are seriously handy.

So let's get started...


What is a filter?

In music production terms, a filter is a device that allows you to remove certain parts of the frequency spectrum from a sound.   They are often used to make the piercing and plain sounds developed by oscillators into more useful synth patches by removing frequencies that might overlap with other synths, meaning they will sit in the mix better and sound much more defined.

A filter usually comprises a frequency knob, to define the point at which it filters the sound, a resonance knob to give access to more wild and wonderful sounds and sometimes an envelope to give more control over how the filter affects the sound over time.

What types of filters are there?

There are lots of filters out there, but some of the most popular ones are...

Low Pass Filters

Useful for: Bass Synths, Pads

These allow you to only let the low end of the sound pass through, attenuating the piercing high end of a sound and leaving you with the pleasant rumble of the subwoofer to fill out the bass end of your productions.

Band Pass Filters

Useful for: Radio effect vocals, mid-range pads

A cool filter that removes both the high and low end around a certain point, leaving a narrow band of frequencies audible which can dramatically change the sound of a synth.

High Pass Filters

Useful for: Lead synths, filter sweeps

The opposite of Low Pass Filters - these only allow high frequencies through.   This is great for making high end percussion or piercing lead synths that give the instrumental hooks of your productions!

Notch/Peak Filters

Useful for: Modulation

Notch and Peak filters cut and boost a small band of the frequencies in the sound put into them respectively.   To make more interesting and dynamic synths, adding a notch or peak filter and linking it to an LFO can add a texture to the synth that makes it cooler to listen to when it's played over a long period of time.  

Some useful techniques

1. Filter Sweeps

By automating the frequency setting of a low, band or high pass filter, you can achieve an awesome sound - reminiscent of when you surface after diving in a swimming pool.   The change in frequency content over time is great for build-ups and is a staple technique in dance music the world over.

2. All-encompassing Telephone Effects

Want a section to be brought down a bit?   To make a part of the song less of a focal point, run it through a band-pass filter and then when you want the music to kick back in, simply turn it off and blammo!   You punch the listener in the face with all the low and high frequency content they were missing!

3. Tidying up your mixes

Ever find your mixes are too muddy?   Try using filters to drastically remove parts of the sounds from synth, giving the other layers room in the mix to shine and not have to fight for precedence in the listener's ears!