ADSR Envelope: 4 Control Elements Used by all Synthesizers


adsr envelope - short tutorial by themusicsensation.comWould you like to learn everything about the ADSR envelope? I have gathered the most important information in this material.

All synthesizers include an ADSR envelope. We are talking about a fundamental concept that underlies the synthesis of all sounds. ADSR is an abbreviation derived from the following terms:

• Attack
• Decay
• Sustain
• Release

I’m about to provide you with a clear definition for each term. It is time to remind ourselves what ADSR means, as it is encountered in all audio synthesis modes. I will explain how these parameters affect each other. I believe a separate definition is not sufficient in this case.

• Attack

Represents the time period in which the sound reaches its maximum intensity after a key or button is pressed. When you set the attack to zero, its effect will be canceled. Due to the absence of attack, decay will immediately begin to make its presence felt.

When you set the attack to a very high value, there will be a very slow rise in volume. What is the role of using attack in a sound? In many cases, we want sounds that start at a lower volume. This often applies to intros.

By gradually and evenly increasing the intensity, we provide a more pleasant sensation to the listener. Imagine how it would be if everything in a musical piece started abruptly. Surely, it would be unpleasant for the listener.

Furthermore, the use of attack creates new possibilities in sound synthesis.

• Decay

Represents the time period in which the sound’s volume uniformly decreases from the maximum intensity to a predetermined sustain level. This happens after it has been triggered by pressing a key or button. Decay is the element that affects the duration of the sound immediately after the attack effect ends.

This is true even if the attack value is zero. Why is decay used in audio mixing and sound synthesis? Imagine how it would be if there was no decay. That means we don’t have the option to shorten the sound’s duration.

All sounds would remain at the same volume. That would make the entire mix flat, monotonous, and even very tiresome. This happens in the case of over-compressed music tracks. Decay creates spatiality in the mix.

• Sustain

It is the intensity level at which the sound remains constant while the key is held down after the sound’s decay period. In this way, sustain determines how long the sound will stay at the same intensity level after decay has occurred. There are two settings here that require further explanation.

If we set sustain to zero, then it will have no effect. Practically, in this situation, we could say that this parameter does absolutely nothing. It’s as if it doesn’t exist on the synthesizer’s control panel. When sustain is set to 100%, then the effect of decay is completely cancelled.

Here’s a relationship between the two control elements:
Any Decay value + Sustain 100% = a sound that remains at the maximum volume level permanently.

Why is sustain a parameter used in audio synthesis?

As mentioned above, sustain comes into play immediately after decay is completed. This control element’s role is to preserve the energy of the sound. We want to have the option to adjust the volume at which the sound is maintained after decay.

When sustain is set to a high percentage, we have rich and full-bodied sounds.

• Release

It is the time period required for the sound to return to zero level after the key is released. In this stage, the sound’s intensity decreases from the sustain level to zero, similar to decay, but the difference is that release occurs after the key is released.

This parameter determines how quickly or slowly the sound will fade out after the key is released. Understanding the relationship between these parameters is crucial.

Let’s see the fundamental role that release plays. Imagine if this option didn’t exist on the synthesizer’s control panel. In that case, you would only have sounds that abruptly stop. Release prolongs the sound slightly. In a musical piece, we don’t want all sounds to end instantly.

Think about how an outro is done. It’s a section that essentially concludes each song. The duration of the sound uniformly decreases until it reaches zero.

The fundamental characteristic controlled by the ADSR Envelope in all sounds.

Undoubtedly, the ADSR envelope is a way to control the duration of all sounds. This principle always applies when deciding whether you want shorter or longer sounds. The second characteristic controlled by it is volume. The intensity is automatically modified by adjusting the ADSR.

Due to changes in the settings, the sound’s intensity is drastically modified at certain moments. The only property that cannot be modified by this system is pitch. For that, within a synthesizer, we have separate control elements.

Fundamentally, there are only three properties of sound: duration, pitch, and volume. There is also the fourth characteristic called musical timbre.

The difference between ADSR Envelope and AHDSR Envelope

Some synthesizers include the parameter “Hold.” It is not necessarily essential; it’s just an additional option that can create more possibilities for sound processing. Most virtual and analog synthesizers do not include this parameter.

I believe it can be worked without it, considering that it is rarely used. Hold is a control element that maintains the sound’s volume at the same level. It is the simplest indicator and does not require further explanations. Here are a few synthesizers that have included the Hold element:

• Sugar Bytes Cyclop

This is a monophonic synthesizer produced by Sugar Bytes. I find it quite interesting and it can be used for dubstep, electro-house, and other genres of electronic music.

Ways to implement the ADSR Envelope in sound synthesis

Let’s see how the ADSR envelope settings are applied to the main categories of sounds in a mix.

• Drums and percussion

Drums are short and powerful sounds. In their case, the decay is set to a low value, and the attack is zero. Sustain and release are also set to minimal values or even zero. This category contains a lot of transients.

• Lead sounds, piano, guitar, and string instruments

The configuration for these is very similar to that of drums and percussion. The attack is zero or may have a few milliseconds. Decay is generally low, and sustain as well. Guitar and piano can sometimes have a release of several seconds.

• Pads and ambient textures

In this category, the attack duration is longer. Pads are a category where the attack is set to a few seconds. Here, all parameters are usually set to higher values.

• Bass sounds

For bass sounds, a lower attack and release are recommended. There is no problem if you use a bit of attack. The issue can arise when the release is set to a higher value. Extending the duration of bass sounds can make the mix very muddy.

• FX (Effects)

These are in contrast to drums. While drums are very short in duration, here we have very long sounds. Effects used in a music mix have a very long attack. This means they start at a very low volume. Their increase in intensity is very gradual. Sometimes, the attack can even have a value of approximately 8 or 10 seconds.

3 Modes of Representing ADSR Envelope Parameters in Sound Synthesis

In sound synthesis, how the control elements are displayed is crucial. This principle applies not only to the ADSR envelope.

• Measuring ADSR values in seconds or milliseconds

Almost all VST plugins indicate the value of the ADSR envelope in milliseconds or seconds. I believe this is the most intuitive way to control their duration. The only parameter that is always expressed in percentages is sustain. This is my preferred method of working with the ADSR envelope.

• Displaying ADSR envelope parameters in percentages

The second category of synthesizers will display the ADSR envelope value in percentages. I find that this implies a limited range of possibilities. The first option seems much more intuitive and practical to me.

For this reason, I recommend choosing a virtual instrument that measures everything in milliseconds. Morphine, an additive synthesizer in FL Studio, indicates these options in percentages.

• 2D graph for adjusting ADSR envelope parameters

The third method is a 2D graph through which you have the option to adjust these parameters. Many synthesizers have used this mode. You manipulate the graph with the mouse to adjust everything.

An example that falls into this category is Harmor in FL Studio. Of course, these graphical representations are accompanied by numerical values. It is preferable for the unit of measurement to be in milliseconds.

Sections Where You Will Encounter These Options in a Synthesizer

You will notice the presence of these options in various sections of a synthesizer. It is important to note that these aspects may vary depending on the synthesizer you are studying.

• Master Envelope

The main section is the Master Envelope. This panel affects all sounds regardless of the number of oscillators the synthesizer has. All synthesizers have a built-in Master Envelope.

• ADSR option used for a single oscillator

Furthermore, you will find a separate ADSR control for each individual oscillator. Modifying these parameters only affects the specific oscillator. This option has been added to allow individual modification of each oscillator.

Here’s a simple and practical example: Let’s say you want to synthesize a preset using two oscillators. You want Oscillator 1 to have a higher decay and Oscillator 2 to have a lower decay.

This combination will expand the possibilities for your sound creation. Of course, this is just a basic scenario. Imagine what is possible when you have six oscillators at your disposal. Moreover, you have the option to modify the ADSR value separately for each oscillator.

• ADSR implemented for sound filtering

In the third case, you will see that the ADSR envelope is applied to sound filtering. A sound filtering mechanism permanently eliminates or reduces specific frequency ranges.

They also serve to open or close a sound. The main filters used are Low-Pass, Band-Pass, and High-Pass. Audio filtering is a separate topic. I will delve into this further in a future article.

What is the connection between transients and ADSR Envelope?

A transient is a short, intense, and powerful component of a sound that occurs at the beginning of a note. You’re probably wondering what the relationship is between transients and the system we’re talking about. Clearly, transients are created by applying the following settings:

• Reduce the attack value to zero.
• Keep the decay at a low duration.
• Completely eliminate the sustain value.
• Set the release to a low value.

By applying this recipe, you will design sounds that have transients. I have already given you some examples of sounds that contain transients above. These include drums, guitar sounds, and plucks. I want to share another practical tip with you that will help.

The shorter the sound, the more it should be emphasized. Conversely, most longer sounds in a mix are kept at a lower volume. This rule is not universal. Certainly, this principle cannot be applied in all cases.

I just want to ask you, what are your ways of using this system? Do you have any tips you would like to share here? How do you apply ADSR in constructing your own sounds? I invite you to leave me a message in the comments box below.

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