filter decay

Easy Synth Programming – More Filter Envelope

Easy Synth Programming – More Filter Envelope

Filter decay and sustain have an amazing level of influence of your end sound.  If you don’t know how to wield the filter envelope’s parameters then you should keep reading.  Pick up a copy of Syntorial for free here.  Why not put my tunes on in the background while u read?

First, the Agony

You don’t realize how much you’re missing out until someone shows you.  Ever though you were cool until your friend showed up with a date?  Not knowing how to use your filter decay and sustain is pretty much like that.

Now, I know you aren’t putting out songs using all presets.  Maybe you are and you’re tired of sounding like everyone else.  Maybe you’re a masochist and you love studying things as opposed to loving people.  Welcome home, friend.

I really hope you are designing sounds on a regular basis.  We are now into the ninth part of a potentially 40 part synth escapade.  If you want to improve your synthesis then start with part one and meet me back here when you’re ready.


We have gone through each part of the synth in minuscule detail.  This may seem frivolous to you but let me argue to the contrary.  Like in math where, if you haven’t mastered subtraction, long division might be impossible, synths will not tolerate your slack butt once you start adding parallel layers of modulation.

Wait, what?  Parallel modulation layers?  Yes, sonny, you heard me right.  If you’ve been thinking about synths as ‘push a key, get a sound’ then you are wrong.  Wrong as a cat winning a dog fight, I tell ya.

Ya see, the synth is a powerful beast.  It has multiple brains which can work at the same time like a Siamese octopus.  The tentacles about which I speak are your modulation sources.  Specifically, I’m referring to several freely-assignable ADSR envelopes.

I Can Haz?

If only you could set your attack, decay, sustain, and release and have unicorn rainbow-like sounds wafting from your near fields.  If only presets were the key to originality.  If only..

If only you could assign an envelope to your filter and make that baby rock!  Ya, baby!  That’s what I’m talking about.  Let’s made the synth do all the work.

We know how to craft the overall contour of the sound by way of the amp envelope.  Usually, that’s assigned by default because synth manufacturers, for all their marketing efforts, don’t trust you alone with an unprogrammed synth.  That’s what I’m here to fix.

Whereas your amp envelope is your sound’s shape, your filter envelope attack and sustain are it’s mood.  They move along the same path – time – but they travel on different dimensions.  The amp envelope walks on volume and the filter envelope struts on frequency.

Parable of the Lions

Like two lions in a pride, they might look extremely similar in that you can set them to be nearly identical.  Indeed, sometimes you can use the same envelope on both the amp and the filter.  However, they can also be very, very different.

Want one lion to be aggressive and pouncy while the other one hangs back to create an intimidating mood?  With filter decay and sustain you can do that and more.  Of course, to play with lions, you need rules.

The main rule for using filter and amp envelopes together is that your amp envelope needs to be ‘bigger’ than your filter envelope.  If your amp envelope is too small then your filter envelope won’t fit inside of it.  Of course, there are exceptions but, as far as being a rule of thumb is concerned, it’s important to remember.

As always, the best way to get started is to get started.  If you don’t have time to read all of my rambling then make sure to get programming using what you’ve gleaned.  For those in search of more detail then the mechanics of setting your filter decay and sustain are below.

Tech Dirt

The first thing you need to do to get your filter envelope game on is to set your amp envelope to a useful value.  Ain’t no sense in setting a filter envelope if you can’t hear anything in the first place.  The filter’s modulation is going to give you something beyond what an amp envelope can do.

After you’ve set your amp then turn your filter cutoff knob down as low as you’ll ever want it for this particular sound.  Now you can set your filter envelope amount to the brightest you want your sound to be.  Remember that this is an offset but it will only work, or be audibly obvious, if you have your filter envelope’s attack, decay, sustain, and release values right.

We’ve already talked about the filter attack and decay.  Those are the outside edges of your sound.  In fact, if you turn your sustain level all the way up then those are the only two parameters which really do anything.

Say When

The filter decay only comes into play if the sustain level is less than 100% max.  This is because the decay, like my tooth metaphor from a previous article, has to decay *to* something.  If something never decays then there’s no decay.

That is a perfectly cool thing to happen if that’s what you want.  If you want that filter swell, then a maximal filter value to hold out while you play, only to then fade back after you release, then leave it like that.  However, if you want your filter decay to do some work and give you that juicy movement you want so much then turn down your stinking sustain level.

There are few different sounds you can get by adjusting your filter decay and sustain, in conjunction with your filter envelope amount.  A very short attack plus a pretty fast decay down to a pretty low sustain will help your sound to have more punch and cut.  Sweeping the filter up that fast gives your sound an edge it wouldn’t otherwise have.

Softly as a Morning Sunrise

Now, if you want more of a pad sound then you can extend the value of your attack and release so you get more of a long swell in and fade out effect.  Even so, if you leave your sustain level at something other than total zero then you will still get another fade out once you release the key.

That being said, unless your filter cutoff is all the way down, you’ll still get an audible sustaining tone even if you have your sustain level at minimum value.  In this case, however, you will not have anywhere for your release phase to go.  Make sure you are trying to recreate a sound in your mind rather than just moving controls randomly or they won’t interact how you want.

There are some advanced techniques regarding the filter decay and sustain.  For instance, in some synths, you can invert the modulation signal so that up is down and down is up.  It’s like bizarro world and it sounds really neat.

Get Big

Try it out on a synth like Native Instruments’ Massive or even on Analog in Ableton Live Suite.  In Massive, you have to assign a free envelope to the filter cutoff.  First assign it a positive value by clicking and dragging upwards on the modulation slot.  Get it working so you can aurally identify the filter’s shape.

Then try dragging the modulation slot down until the blue circle goes counterclockwise from the filter cutoff knob’s indent line.  What you will now hear is the filter cutoff moving backwards through the attack phase until the filter decay moves it back right again to the offset provided by your sustain level.  Once you release the key, your filter knob will effectively move to where it appears on screen.

The more I think about filter envelope modulation via an envelope, the more I think about how the whole setup is just like VCA faders in a DAW.  Interestingly, Ableton Live’s grouping features create VCA master tracks which they call groups.  In that case, when you turn down a group fader, all the internally grouped tracks turn down ‘on the inside’.  You can try it for yourself.

Live for the Moment

Group a drum kit in Live and let it loop.  Send the snare to a reverb return.  Now, as you turn down your drum Group’s fader, you should hear that no more signal is getting sent from the snare to the reverb return.  This is because the group fader is actually controlling each individual track on a behind-the-scenes basis.

I kind of roll my eyes at this feature with Live, though.  I digress but Live simplifies, some might say oversimplifies, some workflow details.  This is a helpful feature for a variety of reasons but learning the details of audio routing is not one of them.

The way that filter envelope modulation is like VCA fader control is that the actual filter cutoff knob on your synth never moves.  The envelope will go through attack, filter decay, sustain and release, and you will hear a difference.  You won’t, despite this, ever see the filter cutoff knob turn.  This is the VCA effect at play.


I’m not entirely sure where VCA faders originated or how they’re technically related to analog synths.  All I can tell you is that the effect is the same.  Kenny Gioia over at Reaper Mania gives an excellent explanation of VCA groups in this video.  He basically describes the VCA fader as ‘turning down little mini invisible faders’ on the slave tracks.

Behind-the-scenes motion brought to you by mastering your filter decay, sustain, attack, release, envelope amount, and positive or negative polarity.  But all these modern sounds have much more going on, right?  I mean, nothing sounds like it did in the 70’s anymore so what’s the secret?

After having completed Syntorial, I was wondering the same thing.  Synths seem to have a million different knobs and options these days so it’s tempting to think that modern sounds use every one.  I’m here to tell you that’s not true.

A, B, C

You see, the fundamentals of synthesis, which you are learning in this Easy Synth Programming series, are going to be in use in virtually 100% of every sound ever.  Of course, some that are taught in Syntorial won’t apply such as pitch envelope, certain effects like phaser, or even polyphonic voicing.

The essential workflow, though, of selecting an oscillator or wavetable, running it through some kind of filter, giving the sound a shape with an amplifier envelope, then adding or not adding effects, will always be happening.  Yet there’s more that synthesizers can do.  Let’s take a look at a few examples before wrapping up.

For instance, in Massive, every assignable envelope has looping functionality.  In fact, even Live’s Analog has similar features.  In Massive, however, the looping is taken to new extremes.  Let’s have a look.

Anytime, Anywhere

Whether you use Massive or not, this should be pretty easy to understand.  Now that you have a basic understanding of envelopes, and how they can be assigned almost anywhere depending on the synth, imagine that you play a note and your envelope goes past the filter decay and onto the sustain phase.  What now?

Well, ordinarily, nothing special happens here.  Typically, you’ll want to rely on other modulations to create interest.  But in Massive, this is different.

The envelopes in Massive can now loop according to a few available commands.  These include how many ‘half loops’ the sustain phase will complete as well as which shapes the loop might take.  Be sure to read Massive’s manual for more details on the shapes.

Forest Full of Trees

Other synths perform looping in a slightly different manner.  In Massive, though, your filter decay will lead to the ‘zero’ point normally when loop is set to ‘off’.  This is typical ADSR behavior.  But if you set loop to 1 then, after your attack, your filter decay will carry out it’s duty in the millisecond value you gave it and then move along another track which you can determine with the shapes I told you about.

I think the best way to think of it is as a pivot point which is right after the filter decay.  By turning loop to 1, you get that pivot point but then can adjust the sustain level that follows independently.  That sounds exactly like what ordinarily happens but remember that now there’s a shape involved.  You definitely need to try it out to get a feel for how it works so pick up your copy of Massive here if you don’t have one.

Another big component of modern sounds lies in the oscillator section.  This article is primarily about the filter decay and sustain but everything from Bro-Step to softer, more subtle textures, make use of waveforms past your standard saw tooth, pulse, and triangle.  I include this here because, by this point, you might be wondering where the vowel basses are.


No vowel basses yet though we will get to wobbles soon enough.  For now, I want to thank my Patrons, the Patron Hexspawn, for supporting me.  You guys allow me to stay at home all day and make Hexspa the best it can be.  Hopefully that means I’m serving you well by creating this tutorial content.

Patrons will be getting additional Ninja Training on filter decay and sustain this week.  In fact, it’s already available as an early release.  In those, for you ‘pubs’, I go into great detail using Massive to demonstrate each week’s techniques.  This week I made a few patches using negative filter values and who knows what else.  It’s great fun so join us over there for $3/mo. or more to get access.

For the rest of you: it takes a metric pluck ton of work to get all these things out to you each week.  While the work can be it’s own reward, a few bucks coming in from PayPal won’t hurt.  I get 12 packs of Sierra Nevada for about $14 so, please, decide how many beers you’d like to buy me and I promise I’ll drink them.

Mess Me Up

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To everyone: thank you for reading, watching, and being a part of my musical journey.  Feel free to share this with your synth friends or anyone who might like my music or other tutorials.  I release content every Monday at 4PM PST so be there!

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