That’s the tool used to control the subtractive part of the synthesis. When you read “multi-mode” it means the filter can act differently so you can choose how the filter behaves. On the Analog Four we have two different filter in series, meaning the sound goes in the first one from the generators, then the overdrive, finally in the second one.
A note on the Overdrive:
Overdrive will Overdriven the sound introducing distortion in the signal path. The Overdrive on the A4 mark one and the A4 mark two are not exactly the same so the sound may differ.
The first one is a 4-Pole Ladder Filter, there’s something you need to know on this one. The default value on the resonance is around 25. That’s important because if you reset this one at zero you will loose some treble and some bass. With the low end in mind don’t reset this filter if you make an INIT Patch.
The second one is a 2-Pole “multi-mode” Filter and you have 5 modes and 7 types : Low-Pass (LP1 and LP2), Band-Pass, High-Pass (HP1 and HP2), Band-Stop and Peak.
The first thing you must have in mind is the Filter in Subtractive Synthesis has many roles. It’s like an actor in a tv-show playing different characters throughout the show by using different disguises.
see i like figure of speech with this metaphor (no comment)
The first role
Act like its word : filtering. So we remove frequencies. If we want to make a Bass sound for instance there’s real chance that we use the Low-Pass (LP1 or LP2) – we hear the raw sound coming from the oscillators and we let the lows pass, we’ll remove the upper extra frequencies we don’t want in our sound. How much we remove will be in conjunction with the oscillator type, if it’s a Triangle we’ll probably remove less than a Sawtooth, because the Saw contains both even and odd harmonics at the fundamental.
Wait! What?
I see you coming… I see you coming… (You heard the song right?)
Fundamental what? The Fundamental is the note you play on the keyboard but frequency wise, there’s a difference in Timbre (or Tone) between an Organ and a Piano. If you compare both of these instruments, the organ will have the fundamental sound and a little bit of energy in terms of harmonics while the piano has more energy in it’s harmonics. That’s why the piano sounds brighter than an organ, will sound more “bassy” – but still the bass generated by the fundamental played in lower octave on the piano will be there. We are tricked by our ears because we focus then on the upper frequencies, we feel the bass but our brains are not focused on the bass any more.
I don’t go into much detail here because there’s other important things to learn – but we will be catching up with that in the next post called : “Frequency matters”.
this a note for you and for myself I guess
A similar concept is if we design a flute patch, we will probably remove the lows on the opposite spectrum, and use a high-pass mode because the flute is not a bass instrument, right?
Another role…
Filters act more like an equalizer, in fact they are part of the same family. If you’re looking to boost certain frequencies you may use a Peak filter. Or, and we’ll discuss now about the resonance and the cutoff point.
You can refer to the filter cutoff point picture. It’s a high-pass filter, we have the slope (note: you’ll have different slope in terms of difference between HP1 and HP2. We choose HP1 over HP2 when we want a more extreme slope) The Red Cross is the Cutoff point. That’s where things become interesting when we push the filter resonance higher, the cutoff point will become sort of a bell and will enhance (like a boost eq instead of a cut) in terms of frequency exactly where the cut-off point is. You can refer to my infocard posted just after this Blog post.
And even download on elektronauts the Filter Table for the Analog Four using the link of this post.
here is the link : https://www.elektronauts.com/files/448
So why all this blabla? You might not have an idea of what I have in mind yet. What I describe to you can actually be used differently depending on what you are after in sound design. You can build a sound using a high-pass filter to design a bass, and take advantage of the cutoff point to act like an EQ and enhance the bass.
Pay attention to the next trick with high pass filters that I will be showing you. This method is more useful in a DAW environment, this technique would really benefit by using a dynamic EQ something like SurferEQ from Soundradix or Fabfilter Q3 can behave the same. The cutoff point of the Analog Four Filter is not dynamic it will not follow the note you play on the keyboard. So this technique will work for couple of keys in the octave range, but as long as you move into another range of frequencies you loose the boost because it’s a fixed value on the Filter.
Maybe it’s a bit complicated for the beginning of this eBook, so keep that trick in mind for later. Let’s move on!
Another role…
A very cool feature about the Analog Four is you have a shortcut in terms of modulation-destination as you have on the Filter Page, a knob called “DEP” and you have it for the Ladder and the “multi-mode” filter! How cool is that? You are smiling reading this, but maybe have no idea about how cool that is. It’s all about envelopes. Maybe you already know about the amplitude volume envelope?
ADSR : Attack, Decay, Sustain, Release ?
Then this shortcut method is already setup to control the filter envelope shape. That’s cool because we use it a lot in Sound Synthesis. It will make the Attack of the sound to appear brighter but not really louder compared to a transient designer on drums (you will have more information on this in the next upcoming eBook called “Layers101”).
It’s very cool because we save time from this shortcut, you also have a shortcut available for the pitch envelope in a later article.
So to quote the manual: “DEP (EnvF Depth) sets the amount of cutoff frequency modulation from the filter envelope EnvF.”
Meaning DEP and EnvF works together. Push this knob and hear how it affects the sound. With that parameter alone while we play a chord, we just have a few more steps to design a Dub Tech Stab or a Stab sound in general because that’s the key component of this sound.
Other acting roles of the filter…
The other role has to do with the conjunction with another set of tools, as we have seen before with the envelope tool. We can pair the filter with an LFO.
LFO’what?
Yeah I know it’s probably too much if you are a new to synthesis, but stay calm. I will focus and explain more as long as we progress through the lessons. The LFO is a powerful tool in your hands. Anytime you read anything on LFO’s get a notepad and practice the concept with your favorite low end sounds like bass patches and kick drums. Taking advantage of the LFO as a sound design tool will require lots of practice to enjoy the benefits of it.
For now just remember this one thing, Envelope (generally) is a one time action, instead an LFO which is a repeated action. A popular effect of an LFO acting on the main volume would be to mimic a vibrato. You can try assign an LFO on the main volume and you will hear a vibrato effect. But hey! You know what you also have a shortcut on your Analog Four for that! How cool is that ?
The Vibrato settings can be found on OSC 1&2 (page 2) you have for that two set of parameter : “SPD” : Vibrato Speed, so it will be slower or faster, depending on your taste. “VIB” : Vibrato Depth, is how profound the movement will be.
So I stoped there for the LFO concept because the Vibrato effect does no longer has to do with the concept of filters.
Therefore when you use an LFO on the Cutoff frequency you have the same effect technically like the Vibrato, but it’s not a volume automation, it’s a filter automation that is acting repeatedly. This is because when we set an LFO, it would be a one-shot modulation. If we set an envelope instead to modulate the filter frequency we have already set the shortcut “DEP” using the filter page.
So let’s move onto “Frequency matters” for now.
