Volcano: Advanced Tactics

PLEASE NOTE: This article has been archived. It first appeared on ProRec.com in June 2009, contributed by then Editor Kim Lajoie. We will not be making any updates to the article. Please visit the home page for our latest content. Thank you!

You’ve probably heard of Volcano – the versatile multi-filter by FabFilter. You might even be using it. As a filter plug-in, it’s pretty deep – four simultaneous multimode filters with eleven different algorithms, multiple routing options, and crazy modulation possibilities. You might think to yourself that there’s enough exploration and inspiration in there for at least a few albums, and you’d be right…

…but that’s not all. Volcano is capable of far more than basic filtering. Browsing the presets, you can get a taste for some of the possibilities but be left wondering; how can this potential be unlocked? How can I use these advanced techniques to set up Volcano for my own music? How can I be awesome?

Wonder no further.


One of the features of Volcano is it’s overdrive capabilities. The labels “In”, “Out” and “Mix” are actually buttons, and the input and output gain controls both range from -36dB to +36dB. Raising the input level allows you to overdrive the filters. In fact, the differences between the filters become a lot more pronounced when overdriven. Some filters don’t distort unless they’re resonant, while others smoothly overdrive even when they’re fully open. Some filters eventually limit the signal once it reaches a certain threshold, while others keep getting louder and louder as they overdrive. Some filters maintain smooth resonance at all levels, while other filters distort more when they’re highly resonant.

Each filter has it’s own characteristics and it’s own behaviour, and there are some complex interrelationships between the original sound, cutoff frequency, resonance, and input level.

Be careful – the input level is not automatically gain-compensated at the output, which means setting levels when using overdrive can be a tricky procedure. You’ll have to keep lowering the output gain as you increase the input gain. This is something that is easier with dedicated hardware than with a mouse alone. Fortunately, the MIDI learn system is pretty painless (simply activate the MIDI learn control, move the on-screen knob you want to assign, and then move the knob or fader on your MIDI controller).

The other thing to watch out for is that the output of Volcano isn’t limited or clipped by default. Audio can very easily go over 0dBFS! If you’re playing with extreme overdrive, make sure your levels are low and/or you have a limiter after Volcano. Your ears and speakers will thank you!

First, experiment with overdriving a single filter. Play around with various filter algorithms, cutoff frequencies, resonance levels, and filter types. Personally, I find the “FabFilter One”, “Raw”, and “Tube” to be the most useful filter algorithms for overdriving. The FabFilter One algorithm is a good first algorithm to try as it’s easy to overdrive and behaves predictably at various cutoff and resonance levels. The Raw algorithm gets a little more raunchy at high resonance levels, but stays fairly clean at low resonance levels. The Tube algorithm is softer and stays warm and smooth even at extreme settings.

Overdriving a single filter

You can already hear quite a variety of distortion flavours by overdriving a single filter. Things can get even more varied and complex when combining several filters. First, start with two filters in series. That is, one filter being overdriven and then being sent through another filter.

One important fact to keep in mind is that the input level is only set at the very start of the signal chain. There’s no straightforward way to apply different levels of drive to individual filters. Another way to think about it is that the input level (and thus the amount of overdrive) is a global control that affects the whole plug-in.

One good filter combination to experiment with is an overdriven low pass filter being sent through a bandpass filter. Experiment with different combinations of cutoff frequency and resonance. Loosely speaking, the first filter determines what gets distorted, and the second filter determines what aspect of the distortion you hear. You can even set the bandpass filter higher than the lowpass filter. Normally, this would give you almost silence, but because the lowpass filter is being overdriven, the upper harmonics being generated are actually above the filter cutoff frequency. You can then use the bandpass filter to isolate the added harmonics and remove the original sound!

Experimenting with Combinations

Some combinations almost sound like guitar amps.

Things can get even more complex with even more filters and routing!

Experimenting with different combinations of filter modes can give some more types of subtle and complex flavors.

Four filters in a row gives you four successive stages of overdrive and filtering. A simple way to use this is as an extreme version of single-filter overdrive – set all four filters to the same algorithm, cutoff frequency, and resonance. Pump the input gain and watch your sound fry! If you’re feeling a bit more daring, you can use different settings on each filter to gradually sculpt the sound over several stages.

Just keep in mind that it’s probably best to start with a fairly broad-band sound, and use the first filter to make a lot of noise. Each successive filter can then gradually cut out parts of the sound. If your first filter is using an algorithm that gets loud as it overdrives (such as Raw or Tube), subsequent filters will also overdrive as they filter the sound.

Four filters in parallel let you use each filter to add to the overall composite sound. You could, for example, have one filter overdriving the bass, two bandpass filters emphasizing the mids, and a highpass filter providing some sizzle up top.

Two dual-filter pipes allows you to craft some more complex overdrive characteristics. You could use one dual-filter pipe (filters one and two) to overdrive the lower frequencies – perhaps a lowpass feeding a bandpass. You could then use the second dual-filter pipe (filters three and four) to overdrive the upper frequencies – perhaps a bandpass feeding a highpass.

A combination with two parallel paths – one going through a string of three filters and the other going through only one filter can be handy if you want to do “parallel distortion” where one path is heavily filtered and overdriven and the other path is somewhat cleaner. This can be a little tricky to balance though because there’s no simple way to adjust the relative volume of each chain.

A combination with three parallel filters into a single fourth filter can be handy if you want to use parallel overdrive and then run the whole lot through a final filter to tame some of the higher frequencies.

There are even more routing options available. Experiment and use your imagination!

Mid/Side Processing

Mid/Side Processing is a method of treating stereo audio as two channels, but instead of Left and Right, they’re Mid and Side. The Mid channel has the part of the sound that is in the middle (the sound that’s common between the two speakers) and the Side channel has the part of the sound that makes it stereo (the sound that’s different between the two speakers).

To hear what this can do, run some stereo sounds into Volcano, and switch it into M/S mode. Here, the first filter is processing the Mid channel and the second filter is processing the Side channel. Make sure both filters are set to low pass, and the cutoff frequencies are as high as they can go. Now slowly lower the cutoff frequency for the second filter. You should hear your audio being collapsed to mono. This is because the Side channel (the stereo part of the sound) is being filtered out.

Try the same with the first filter. Your audio should sound hollow as the center part of the sound is being filtered out (leaving only the stereo part of the sound).

Now try experimenting with resonant filter sweeps. Sweeping the Mid channel should sound solid and centered, but sweeping the Side channel will sound like the sweep is coming from behind you or outside your speakers!

Outside of psychedelic effects, Volcano’s Mid/Side mode can be used more subtly. For example, you could use it as a widener/exciter on a dull mix. 

Pseudo Stereo

Volcano also has a L/R mode where each side of the stereo sound can be processed independently. That means you can have different filter settings for the left and the right. One handy use for this is to add width to a sound and even turn a mono sound into a stereo sound.

One classic way of doing this is to apply a lowpass filter to one side and a highpass filter to the other side. This was used famously on the Beatles’ song “I Am The Walrus” (listen to the second half, after the radio tuning sound). Another method is to delay one side. This often makes the sound appear to come from one side, unbalancing the stereo spread. But you can use Volcano to overcome this by slightly lowpassing the side that’s not delayed so it becomes a little quieter and duller than the other side. Try it!

Of course, you can also use this mode while doing “regular” filtering to add a little stereo spice. And then there’s modulation to try.


Despite being primarily a filter, Volcano can do some pretty convincing chorus and flanger sounds. This is because each filter has it’s own delay which make it sound up to 50ms later. What’s more, the delay time for each filter can be modulated by an LFO… and an LFO-modulated delay is the basic building block for pretty much every chorus and flanger out there!

To get started, load up Volcano with two filters in parallel.

If you adjust the delay time for the first filter, you should be able to hear the comb-filtering effects distinctive of chorus/flangers. Now, add an LFO and assign it to the delay time of the first filter. The pitch is pretty wobbly at first (like a broken record or tape), so slow down the LFO to about 0.500Hz and the modulation level to about 0.010. You should hear some pretty tasty flanging (it helps if you’re processing audio that is bright and has a lot of energy in the high frequencies).

You might notice that the pitch isn’t changing for half the LFO cycle. That’s because the LFO adds a positive AND negative offset to the delay time, but the delay time is at zero so it doesn’t change when the LFO is in the negative cycle. To get a smoother LFO sound, set the delay time for the modulated LFO to about 0.5ms (half a millisecond), or until you hear a smooth LFO cycle.

You might find that overdriving Volcano makes the comb filtering more prominent. If you set both filter algorithms to “FabFilter One” and boost the input level until the sound is distorting, you should hear a distinctive “jet” flanger sound!

To get more mellow chorus sounds, use delay times of about 15ms. You’ll probably also need to increase the modulation level to about 0.1. You can make it even more mellow by lowering the cutoff frequency of the first filter (the one that’s modulating) so that the modulated sound becomes warmer. Once you’ve got the hang of that, you can then start to experiment with richer chorus sounds by adding more filters! Set up four filters, each with their own LFO (at slightly different speeds).

LFO Gate

We’ve already started to have a look at how Volcano’s LFOs can be used to produce interesting chorus/flanger effects. Compared to regular LFOs though, Volcano’s LFOs are very flexible and play a big part in creating other effects you might not expect from a filter plug-in!

One such trick is using an LFO to turn Volcano into a rhythmic gate! Add an LFO and assign it to the input knob. Make sure you turn the output level down though – otherwise the output will be quite loud! Then set the “Glide” knob from it’s default maximum value to midway, and you should see and hear the LFO shape morph from a sine to a square. Now just set the speed of the LFO to sync at 1/16 and change the polarity of the LFO by swapping the two sliders so that the first is at the top and the second is at the bottom. Voila! Rhythmic gate!

By using different combinations of settings for the LFO values and the modulation level, you can go from mild pulsing to rhythmic distortion (where “on” beats are more distorted than “off” beats). You can also achieve gating effects by assigning the LFO to a filter instead of the volume level. By reducing the modulation level, you can even make it sound like only part of the frequency spectrum is being gated.

Sequenced Gate

Sure, that rhythmic gating sounds pretty great, but it’s a little boring. What if we didn’t have to be limited to simple square waves? What if you could make a sequenced gating pattern? Well, I’ll let you in on a little secret about Volcano’s LFOs.

There’s a  “+” tab on the right hand side of the LFO.

Click on it.

Ignore the two knobs on the right for now. Focus on the LFO shape window in the middle where there use to be two sliders, now there are three. Press the “+” a few more times – you can have up to 16 sliders.

See where this is going? Hehe…

If you pull up all the odd-numbered sliders and slow down the speed to 1/2, you should get something that sounds like what you had before! This time though, you can make sequences that are much more rhythmically complex. Once you start combining several sequencer/LFOs with several filters, you can imagine the possibilities. And once you add in the other effects Volcano is capable of, such as self-oscillation, chorusing, and overdrive, you begin to really appreciate the depth of the plug-in.

Fast LFOs

LFO usually stands for Low Frequency Oscillator, but the LFOs in Volcano can get to some pretty high frequencies – up to 500Hz in fact! That’s “audio rate”, and can make some pretty interesting sounds when modulating level and filters at those sorts of speeds. Normally, audio rate modulation of amplitude (volume) is known as “ring modulation”, but Volcano can take you far past the usual Dalek noises!

Dynamic Processing

As if LFOs weren’t enough, Volcano also has envelope followers too! The obvious application for this is to create an envelope filter effect by making an envelope follower control filter frequency. Normally this is a rather uninteresting sound, but when you factor in self-oscillation, multiple parallel (and serial) filters, and multiple envelope filters (each with their own attack and release speed), you’ll find you can easily move past the regular envelope filter sound.

Things start to get VERY interesting, however, when you start to use the envelope followers to control other parameters…..like volume!

Because modulating volume can sometimes make things VERY loud, it’s a good idea to turn your speakers down and be careful! The envelope followers can be very sensitive and very powerful, making it possible to completely twist the dynamic behaviour of the audio into something new! Also keep in mind that the mix knob is there too – it can be useful for getting a more subtle effect.

Some of the effects you can get are:

· Inverse/slow attack – by setting the attack time to zero and using negative modulation. Use the ‘-‘ button on the lower-left of the modulation amount knob.

Start with the modulation amount at zero and slowly increase it until you hear it sucking the attack of your sound!

· Transient punch – Start with the slow attack sound as above, and gradually increase the attack time. Slightly increase the modulation amount for a more pronounced effect

· Compression – Start with the slow attack sound, but adjust the mix level so it’s not 100% wet. A good way to do this is to start with the mix at 0% (completely dry) and gradually increase it until you hear the compression effect.

Because the envelope followers can be so sensitive, the settings for various effects depends entirely on the nature of the audio you’re processing, mainly it’s level and speed.

Once you’ve got the hang of that, you can start to experiment with some of the other effects that Volcano is capable of. Instead of being static, or being modulated by a regular LFO, you can make them respond dynamically to the sound by using an envelope follower.

Go Forth And FSU

There you have it! You now have the building blocks for taking Volcano far beyond mere filtering effects. Remember to keep experimenting and combining these approaches. Some truly unique and interesting sounds can be found by having two or three different effects all moving together as one. Imagine a distortion processor, a chorus/flanger, a ring modulator, and stereo enhancer… all interconnected and responding to the same bank of LFOs and envelopes!

And when you’re through with that, come back because there’s even more in Volcano that I haven’t told you!