Become a member
Become a member

or
Continue with Google
Log in
Log in

or
Log in using a Google account
learning

Send It in an Envelope

Sound synthesis, sound design and audio processing - Part 8

We have started to study the way in which you can create a sound with the aid of a hardware or virtual synthesizer. But, how does sound ─ which is up to now a combination of voltages or binary data packages ─ turn into something you can actually hear?

View other articles in this series...

Well, it goes through what is called…

The amp stage

Which consists mainly of two elements: An amplifier and an envelope (but not the kind Granny sends you letters in) to control it.

Just like with oscillators and filters, the amplifier can be analog (Voltage Controlled Amplifier – VCA) or digital (Digitally Controlled Amplifier – DCA).

The envelope is used to define the behavior of the amp through time. It’s the last processing stage before the sound leaves the synthesizer and, as we will see, it can have serious consequences. Depending on the settings of the envelope, sound can be more percussive or smooth, immediately or progressively audible, short and effective or long and atmospheric…or many other things.

While there are many kinds of envelopes, the most common type has four elements: Attack, Decay, Sustain, and Release, and it is consequently called an ADSR envelope.

Attack

The attack defines the time elapsed before sound rises to its maximum level.

Here’s an example of a sound with a short attack (meaning it reaches its maximum level right away), followed by the same sound with a long attack. 

00:0000:00

 

00:0000:00

Short attacks are best to create immediately audible, twangy sounds. On the contrary, pads and ethereal sounds require a longer attack time.

Decay

The decay time determines the time required for the sound to go back down from its maximum level, after having reached the latter in the specified attack time.

In the previous example, there’s no decay, the sound always stayed at its maximum level once it had reached it. Introducing a decay allows you to give movement to sound, like in the following example where I combine it with a long attack:

00:0000:00

Or even to emphasize the attack, at the cost of reducing the overall sound volume, like here:

00:0000:00

This volume reduction is not just an impression because if you say decay you say sustain reduction.

Sustain

The sustain is the volume level you want the sound to maintain after the attack and decay, and which ought to remain constant as long as the note is pressed.

You have surely heard the sustain in the previous examples (the sound after the attack and decay, as I just said!). Here’s the result of audio example 2 with a very low sustain level.

00:0000:00

Oh, yes, it’s almost like a percussion sound!

Release

Finally, the release determines the time needed for the sound to turn off completely once you let go of the note.

In the previous examples, the release time was zero, which means the sound was immediately muted as soon as I stopped playing the note. Now I’ll retake the sound from example 1, which has no decay, but with a sustain of about 3 seconds and a release timeof more than 7 seconds:

00:0000:00

The release is triggered as soon as you let go of the note (or a “note off” message is sent to the synthesizer ─ which is something we’ll come back to later on), even if the rest of the envelope wasn’t played.

For example: If the attack of a sound was set to 2 seconds, but the note was released after only 1 second, the end of the attack and the decay will be skipped, while the sustain period will obviously be non-existent. The only thing left will be the release.

Some general considerations on envelopes

Logically, the attack, decay and release values are almost always in the milliseconds and the sustain value is often expressed in a scale from 1 to 10 or 1 to 100. The length of the sustain depends solely on the time the note is played, once the attack and decay times have elapsed.

This is how an ADSR envelope is usually represented:

Some synthesizers feature variants of the ADSR envelope, like the Yamaha DX7, which features envelopes with eight parameters.

Other synths have a “hold” parameter between the sustain and the release. It allows the musician to disengage the note and focus on other parameters of the synth without triggering the end (release) of the note played. This allow you to send particularly long messages, in order to create sonic pads or evolving effects, like wind simulations, for instance.

While envelopes are usually found in the amp stage, they are also used sometimes to control the behavior of filters and even some other parameters and effects.

← Previous article in this series:
Filter It Out!
Next article in this series:
A Mono/Poly Game →

Would you like to comment this article?

Log in
Become a member
cookies
We are using cookies!

Yes, Audiofanzine is using cookies. Since the last thing that we want is disturbing your diet with too much fat or too much sugar, you'll be glad to learn that we made them ourselves with fresh, organic and fair ingredients, and with a perfect nutritional balance. What this means is that the data we store in them is used to enhance your use of our website as well as improve your user experience on our pages (learn more). To configure your cookie preferences, click here.

We did not wait for a law to make us respect our members and visitors' privacy. The cookies that we use are only meant to improve your experience on our website.

Our cookies
Cookies not subject to consent
These are cookies that guarantee the proper functioning of Audiofanzine and allow its optimization. The website cannot function properly without these cookies. Example: cookies that help you stay logged in from page to page or that help customizing your usage of the website (dark mode or filters).
Google Analytics
We are using Google Analytics in order to better understand the use that our visitors make of our website in an attempt to improve it.
Advertising
This information allows us to show you personalized advertisements thanks to which Audiofanzine is financed. By unchecking this box you will still have advertisements but they may be less interesting :) We are using Google Ad Manager to display part of our ads, or tools integrated to our own CMS for the rest.

We did not wait for a law to make us respect our members and visitors' privacy. The cookies that we use are only meant to improve your experience on our website.

Our cookies
Cookies not subject to consent

These are cookies that guarantee the proper functioning of Audiofanzine. The website cannot function properly without these cookies. Examples: cookies that help you stay logged in from page to page or that help customizing your usage of the website (dark mode or filters).

Google Analytics

We are using Google Analytics in order to better understand the use that our visitors make of our website in an attempt to improve it. When this parameter is activated, no personal information is sent to Google and the IP addresses are anonymized.

Advertising

This information allows us to show you personalized advertisements thanks to which Audiofanzine is financed. By unchecking this box you will still have advertisements but they may be less interesting :) We are using Google Ad Manager to display part of our ads, or tools integrated to our own CMS for the rest.


You can find more details on data protection in our privacy policy.
You can also find information about how Google uses personal data by following this link.