What Is ADSR in a Synthesizer? Quick Guide

If you are working with synthesizers, as I do with my beloved OB-6, it is essential to understand the concept of ADSR, which refers to the envelope of a sound. The ADSR envelope is one of the most important components of the synthesizer, as it determines how the sound evolves over time. In this quick guide, I’ll explain in simple terms what ADSR is, how it applies to the amplifier and filter, and how you can use it in your music.

What is ADSR in the Amplifier?

The amplifier’s ADSR controls how the volume of the sound changes from the moment a note is played until it stops. This adjustment is crucial to defining how a sound begins, sustains, and ends. Let’s break down each parameter:

Attack

Controls the time it takes for the sound to reach its maximum volume after the key is pressed. An instant attack makes the sound start immediately at its maximum volume, while a slower attack creates a smooth fade-in.

Decay

Determines the time it takes for the sound to drop from the maximum volume (achieved during the attack) to the sustain level that will last as long as the note is held. A short decay will make the sound drop quickly, while a longer one allows for a more gradual transition.

Sustain

This is not a time but a volume level that is maintained while the key is held, after the sound has gone through the attack and decay phases.

Release

Controls the time it takes for the sound to fade out completely after the key is released. A short release makes the sound stop almost instantly, while a longer release creates a more extended fade-out.

ADSR or Envelope Applied to the Filter

The ADSR can also be applied to a synthesizer’s filter. Synthesizers, both hardware and free and paid virtual instruments, usually have a frequency filter that modulates the sound’s frequencies. In this case, the envelope parameters don’t directly affect the volume but rather how the sound’s frequency content changes over time. (For instance, the classic filter sweep in electronic music tracks, where high frequencies gradually appear, leading up to the drop, one of the main parts of an EDM song).

Here’s how the envelope affects the synthesizer’s filter:

Attack (Filter): Determines how long it takes for the filter to reach its maximum openness after the note is played. For example, a short attack will quickly open the filter, letting high frequencies in immediately.

Decay (Filter): Sets the time it takes for the filter to close from its maximum openness to the sustain level.

Sustain (Filter): Defines how open the filter remains while the note is held. A high sustain keeps more high frequencies, while a low sustain allows only lower frequencies to be heard.

Release (Filter): Controls how long it takes for the filter to fully close after the key is released. A longer release allows high frequencies to fade out gradually.

Practical Use of ADSR or Envelope

You can experiment with the envelope using any of the best synthesizers and countless free plugins, not just synths but also EQ filter plugins. In the video, I show practical examples of how each envelope parameter works and how I apply ADSR in a new music production for my project Tripulante. For this track, I’ve set the release to a relatively long time on the amplifier, allowing notes to blend smoothly, creating an immersive texture.

Conclusion

Mastering ADSR control in both the amplifier and filter is fundamental for shaping the character and dynamics of a synthesizer’s sound. Put on your studio headphones and experiment with these parameters to create unique sounds and adapt them to various musical styles. Don’t hesitate to try different configurations to find what best suits your creative needs!