In subtractive synthesis filters play a Monumental role as they are the tool that subtracts frequencies in order to derive a new sound. Getting to know filters well will transfer over into other synthesis types as well as mixing techniques as an EQ is essentially a filter and is used on almost every track of a production to shape the frequencies being heard.

Let’s look at a low pass filter to demonstrate some of the common parameters to familiarize yourself with.

First is the cutoff frequency which sets the point where the filter begins to remove audio. in the case of a low pass filter audio above the cut off is removed while audio below the cut off will be heard. as the name suggests this type of filter allows the lows to pass.

The Resonance parameter creates a frequency boost at the filter cut off. this will accentuate the frequency of the cutoff. Turning resonance up helps to really bring out the sound of what the filters doing and is a useful tool in sound design.

Most filters also have some options for the slope of attenuation or how quickly the filter will remove sound. this slope is expressed in DB per octave. the more DB per octave that the filter cuts the faster you remove sound and the more aggressive the filter will behave when resonance is applied. That is the difference between the -24 and -12db lowpass filter options within analog.

Filter Slope is Measured in Decibl (dB) of attenuation per octave or dB / OctThis is also sometimes described in terms of Poles as shown below:

• -06 dB per Octave = 1 Pole
• -12 dB per Octave = 2 Pole
• -18 dB per Octave = 3 Pole
• -24 dB per Octave = 4 Pole