Controlling the volume envelope

Now that we know how envelopes of different sounds look like, it’s time to tweak Clearsynth and find out how different envelopes sound like!

Set Clearsynth to the basic saw preset. We’ve seen the envelope of this sound in our previous tutorial to be something like this.

Image 1: Default saw preset

Observe the panel at the bottom right corner of Clearsynth called Envelopes. There are many knobs here, but some of them are already familiar: attack, decay, sustain and release. However, there are two knobs of each! That’s because this panel can generate two separate envelopes. Each of these two rows of knobs allows us to control these two envelopes separately. Now, why would we need two envelopes?

What we learnt in our previous tutorial is just one type of envelope: the volume envelope (also commonly called the amplitude envelope). There are other types of envelopes possible, and more things we can do with them. But that’s for later. 🙂

Now, focus on the bottom row of ADSR knobs. That’s the one that helps us adjust the volume envelope.


In the saw preset, the attack knob is turned to zero. See what happens when you increase the value of the knob. The sound builds up in volume more and more slowly as you increase the value. What you are controlling with this knob is the time of the attack phase. The greater the value of this knob, the longer it takes for the sound to build up to the maximum value. At about 60%, the s(M)exoscope shows the waveform like this.

Image 2: Waveform with increased attack

Here is a small sound clip that has a single note played, with a gradually increasing attack value.


Let’s look at the Decay knob now. Just like the attack knob controls the time duration of the attack phase, the decay knob controls the time duration of the decay phase. Set the attack knob to 50% and play around with the decay knob, to hear how it sounds.

Here is the waveform with the decay knob set close to the middle.

Image 3: Waveform with an increased decay value

And here is a sound clip with the decay value starting from zero and gradually increasing.


This knob is slightly tricky. Remember that the Sustain phase lasts for as long as you press and hold the note. How can you control the duration then?

Well, you cannot. It is entirely dependent on the note played. Play a short note, and the sustain phase is short. Play a longer note, and the sustain phase is longer. What is this knob doing then? It is actually controlling how loud the sound has to play when the sustain phase is reached. So, while the other knobs control the time duration, the sustain knob is the exception. It actually controls the volume, or the amplitude of the note played during the sustain phase.

Try reducing the value of the sustain knob as you play a note. As the value reaches zero, the sound becomes short notes, no matter how long you press and hold the key.

This is how the sound looks with zero sustain. Notice that only the attack and decay phases are visible.

Image 4: Waveform with zero sustain

Here is a sound clip with the sustain value gradually reduced towards zero. The length of the note I play isn’t changing. But as the sustain value decreases, the complete duration of the note sustain becomes less and less audible, until it finally disappears, and you hear just the attack and decay.


This knob controls the duration of the release phase. Using this, we can make the synth play the note for sometime even after the key is released. If the note has to stop immediately after the key release, the knob has to be set to a very low value, or even zero. Having a good release time makes the end of the note less abrupt.

Here is a sound with a long release.

Image 5: Waveform with an increased release value

This sound clip plays notes with gradually increasing release time starting with the release time of zero.

Now that we understand how to control the volume envelope, in the next tutorials I’ll be taking about something which is probably more important when it comes to learning synths. The standard “when to use what” question. I’ll also try to answer a few common questions asked about volume envelopes. Keep reading!

Note: If you are having trouble playing any of the audio clips, drop me a comment and let me know.


5 Responses to “Controlling the volume envelope”

  1. 1 Poppa!
    January 13, 2010 at 10:20 am

    Strangely none of these clips are playing. Similar flash based controls on other sites work as expected for me though.

  2. 5 Smar
    February 2, 2010 at 7:30 am

    Great lessons so far, i have already learnt alot thank you very much, the audio works fine for me on this page.

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