Using Filters for Compositional Variation
By: Michael 'Myk Eff' Filimowicz
Tags: Technology, Music Production, Audio, Culture, Ideas

Today we can do more to vary our compositional elements than flip our melodic lines upside down, run them backwards or nudge them upwards or downwards as per classical techniques such as line inversions, retrogrades or transpositions either within the same or to other keys. Signal processing adds near-infinite possibilities for tonal variation. While utilizing a plethora of audio effects may not seem like fugue method per se — since we cannot systematically exhaust the material given the vast multitude of methods achievable with today’s toolset — we can take some ‘fugue-al’ inspiration from the idea of repurposing compositional material through exploring and integrating sonic mutations. Mutations on a theme, rather than variations, is probably a more apt phrase to use in the context of the ‘pluginscape,’ which is its own kind of soundscape for music and audio production.

This article will touch on a few techniques and tools for using filters compositionally, rather than discuss the usual topics associated with filters, such as dB slope, cut-off frequencies, resonance, types of filters etc. Those topics cover the ‘how’ or ‘what’ aspects of filters, but leave out the ‘why’ and ‘when’ dimensions. I will not exhaust the why and when here in any kind of systematic treatment, but hopefully you may get some ideas for using filters in your compositions in ways you may not have used them before.

Routine Filter Sweeps

Probably the most common creative use of filters is to gradually add or subtract frequency content over time as part of a riser or paradoxically named ‘downlifter’ element in electronic, especially dance-oriented, music. Given the prevalence of this genre-routine, that seems to be a good place to start for the compositional use of filters, which is distinct from other uses that serve more practical or psychoacoustic purposes, such as dealing with problems of instruments masking each other when they share common spectral regions with parametric EQs.

In this first example set, there is a pitch pattern that occurs early in my (somewhat literally named : ) piece Minimal Psy Glitch Walking Bass without a filter treatment, which then gets the temporal and spectral addition and subtraction when it appears later on. Here’s the pitch pattern the first time it is introduced:

Later in the composition, this same pattern is reused but with a filter sweep that first adds, and then subtracts, its spectral content. In the latter part of the sample, you can also hear (and see!) the pumping effect as its amplitude is modulated by a kick drum (unheard) happening elsewhere in the mix:

As this is a rather straightforward use of automating a filter’s cutoff frequency, I would tend to use a straightforward (but still great sounding!) tool like Waves’ OneKnob Filter. Below, you can see the filter adjust as a DAW automation track changes it over time.

Towards the beginning of the video, you can also see that shortly after the knob starts moving, the thin purple ring that borders it lights up — this is because the filter’s bypass (turning it off and on) is also being automated. With filter effects, you often want to turn them off and on when you start using them for more expressive purposes, so that you can easily use versions of the instrument with and sans the filtering.

The automation heard in the Pitch Pattern | Filtered example above.

Narrative Arcs

The concept of a narrative arc is that over time, the emotional intensity of events should rise and fall, typically with a climactic moment of some kind towards the end of the story, and at the top of the arc.

A Narrative Arc. Image Source

The rising and falling of a filter shown above can also be used in this narrative intensity-building way, since as sounds become spectrally duller they also typically become less intense or dramatic from an emotional perspective.

Towards the ‘climactic’ end of my track Cosmic Ray Juice (the link below will take you to the right moment in the mix), I bring in an automated filter that has a rhythmic rather smoothly varying character.

There are many ways to use filters rhythmically, which in itself points to an interesting aspect of contemporary music that is distinct from previous musical eras — namely, that it’s very easy for sonic features to migrate across compositional territories. Spectral content is normally associated with the acoustic and musical concept of timbre, not rhythm, but filters can modulate timbre so that it becomes more beat-like in character. Today, these category crossings happen with every aspect of music because of the affordances for manipulating every sonic parameter — another example would be beat-making practices where the percussive elements become more melodic because of the capacity for changing the pitch of samples and MIDI notes on a per-beat basis.

The rhythmic filtering in the example above was done in this instance with Waves’ MetaFilter plugin, which is shown below in action during this ‘climactic end’ of the music. In the video, the MIDI clip controlling the virtual instrument being processed was moved later in the timeline, which is why you see the filter working for some 15 seconds before the audio actually starts to be processed (as shown in the pairs of Input and Output meters at screen right). Note that this filter is actually being used to modulate the filter’s dB parameter, and all frequencies are actually being passed through!

Modulating an all-pass filter’s dB .

Filter and Rhythm

Of course, normally we don’t use filters to pass through all frequencies and just change the signal level! In the examples below, there is an unfiltered pitch pattern, followed by its ‘filter-rhythmized’ doppleganger. This is also an example of thematic mutation as discussed above.

In electronic music, much pitch content lies somewhere conceptually between melody and arpeggio (and rhythm!). I tend to think that if a pitch pattern cannot be hummed easily, it’s not a melody per se more like a rhythmic articulation of harmonic space, i.e. a pattern of broken up sequentialized chords (or something like that). The MIDI notes of the two examples above are shown below in the piano roll — you can decide for yourself whether this is a melody or arpeggio or pitched rhythm etc.