Join Evan Sutton for an in-depth discussion in this video Filter routing and signal flow, part of ABSYNTH: Synthesis and Sampling.
- Now that we've got our oscilator set up and we're wrapping our heads around it a little bit, let's take a look at the filter section. In order to instantiate a filter, let's bring it up right here. I'm gonna click on it. Right now it's on cloud, but let's just go up to a simple low pass filter. You may be thinking to yourself, 'Evan, what's the deal with these low pass filters?' We've got 2, 4, 8 and then we've got these low pass filters down here; - 6, -12, -24, and so forth. Well, let me tell you there is a difference between these sets of low pass filters.
If you're scratching your head as to why that's confusing, then it's actually because low pass filter 2 pole and -12 dB technically mean the same thing. When we use the word poles, we're actually talking about the angle or the severity at which the filter cuts off the frequencies above the cutoff. If it's a low pass filter, it's going to attenuate frequencies above the cutoff frequencies and the poles actually set up the severity at which those frequencies are cut off. So, let me just grab a 4 pole and I'll play it (low humming) And I'm actually gonna adjust the amp envelope here so it's just kinda sitting there.
Go back. (low humming) Alright, now I'm gonna switch it to a 2 pole. (low humming) It's the same cutoff, but the 2 pole is less steep so we're getting a touch more high frequencies. This also is going to change the way the resonance sounds. Now, a 2 pole cuts off frequencies at 6 dB per octave per pole, okay. So, that's 12 dB per octave. A 2 pole filter cuts off frequencies at 12 dB per octave. 4 pole cuts off frequencies at 24 dB per octave; 6 dB per octave per pole.
8 pole is 32 dB per octave. When we see -12 dB, that can be a little bit confusing because 2 pole does mean -12. Well, I'm just here to tell you that the ones that say pole are meant to have a more analog style sound. Pole was a word that was quite often associated with moog filters. So if I set this up to the 4 pole, and I move the frequency. (low humming) Let's add some resonance.
Nice and juicy. Let's switch it over to the -24 dB, which is a more digital modern sounding filter. (humming fluxuating) I'll just leave it on the same frequency. Let's go ahead and just switch it over. (low humming) You can hear that the analog filter has a little bit less bite to it. That's how I describe it at least. They just have different character. Experiment with using different ones for different sounds. If you're stumped as to which one to use, just follow your ears.
So now that we've got this low pass -24 dB set up, I'm gonna open it all the way up to 22,000 hertz and I wanna set up an envelope to modulate it. You must think I'm crazy. Well, in reality, it's not a whole lot of fun sitting here with a mouse moving this up and down, back and forth, and it's very expensive to hire people to do that all day long while I'm making music. So, I'm gonna right-click here on the parameter that I wanna modulate with an envelope. If I go all the way to the bottom of that menu, I'm gonna see Create A New Envelope.
I'll do that one more time. If I wanted to modulate resonance, I could do the same thing. The pitch of this oscilator, I could do the same thing. But I want to do the frequency of my filters. So, I'm gonna right-click here, go to Create A New Envelope, and it's gonna take me to the envelope screen. You notice that I now have a new envelope populating this envelope menu down here. My Oscilator A amplitude envelope is still there. Let's pull in the release a little bit. When these envelopes get instantiated, they don't always look like envelopes.
Right now, this is just a straight line, but I'm gonna pull them down to zero. At least the attack and release down to zero. And you'll see that now it looks a little bit more like an envelope. Let's listen to it. (various humming noises) That's pretty cool. Let me switch this back to single mode. (various humming noises) Nice, brassy, heavy filter. We can turn up the resonance if we want even more.
(various humming noises) Really brassy, really heavy. Now, you may be thinking, 'That's cool, but it's kind of harsh. I'd like to to not bring the cutoff frequency up quite so high.' Well, here's how we do it. We can either move the top point here in this envelope down. Oh, by the way, you're always gonna see the read-out of each break point that you click on as it relates to the parameter that you are adjusting.
So, up top in this menu here, we can see the actual time that it has. We can see the hertz and we can see the slope, which relates to the node there. Let's jump back to the patch screen. Now, if we want this envelope to not take the cutoff quite so high, we can actually just pull the cutoff down. The amount that we set here is actually going to set the range of modulation for the envelope. So, if it's up at 22,000, and we have our break point for the attack all the way up, it's going to basically be as close to 22,000 as it's gonna let us get.
Now, if I start to pull this down, 7, 7, 7, 8, then you're gonna see that that break point now represents that amount. And we can hear it too. (various humming) We can pull it down even more. That resonance is kinda harsh. (various humming) Let's do the analog filter.
Now let's see what that sounds like. (various humming) You know what, I had the randomness up a little bit on here so we were getting some wacky pitches. (various humming) Not too bad now, huh? So, that's our basic filter. We also have high pass filters, which are super handy and fun. A high pass filter is going to cut off frequencies or attenuate them below the cutoff.
And the slope basically works the same way. Here's a high pass filter -12 dB. (high pitched humming) Let's bring that range of modulation up. (humming) And we also have a band pass filter. (multiple hums) Now, all of these filter types can be set up to modulate in semi-tones as they relate to the hertz.
This is a little bit of a different method for modulating a filter. I don't use it very often, but it is there and it's something worth trying out if you're looking to change up how your filter is modulated. Let's go back to the low pass. So, I have this double wave-form that I can do. I'm gonna make what I call the starry night patch. Oh Evan, this is so magical. Let's take my saw-tooth. We've got two saws. And I'm just gonna de-tune them slightly. Let's get rid of the filter for now. (low humming) So, we're getting some slight phasing here.
Let me play a chord. (electro sound) When we de-tune them apart a little bit, we get that nice phasing action. It feels very romantic to me. (electro) You don't wanna go overboard to the point where you're actually losing the music, but making things really lush and thick can be really cool. (electro) So, let me go ahead and bring in my filter now. Let's really magic this thing up a little bit. So, I'm gonna turn this up and let's add a little resonance. I'm gonna do 4 pole.
Here's my filter cutoff. (electro sound) Okay, that's a little less romantic because it's too quick. We want the moment to last. It's about savoring life. So, let's extend the decay. We're not changing the overall timbre of the sound too much because we're still starting in the same place, the sustained level is basically at the same place, but we're really milking that decay time to give us some nice movement over a long period of time. And, let's also turn the release up a little bit.
Let's do the same for our amplitude so we can hear that release, and let's take a listen. (electronic humming) Not too bad, huh? So that's basic filter routing in Absynth. Just remember that if you wanna modulate something with an envelope, you just have to right-click on the parameter and click Create A New Envelope at the bottom.
- Routing and signal flow
- Destructive envelope editing techniques
- Beat syncing and envelope looping
- Basic sampling
- Master FX