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Basics of Synthesis: Envelopes

Hello again, Tom here! If you’re new here, welcome. Today I’m going to be continuing on with my Basics of Synthesis series (see the first instalment here). This time, we’ll be focusing on envelopes.


Hopefully you’ve found a great synth tone that you like by using the information on oscillators and waveforms that we covered last time out. The next step is to add articulation and ‘shape’ the sound. We can do this by utilising what is called an envelope.


Have you ever seen the letters ADSR, written in that order? Or maybe you’ve heard your favourite producer on YouTube mention words like ‘attack’ or ‘sustain’ and wondered what they mean? Modern envelopes will often incorporate 4 parameters: Attack, Decay, Sustain and Release. I’ll start by discussing these individually.


Attack essentially describes how quickly your sound reaches its maximum volume. For example, you might use your attack parameter to fade the sound in over the course of 1.5 to 2 seconds - leaving you with a lush, pad-like sound. Or you could use it to max out the volume in a matter of a few milliseconds, which could help you create a plucky lead or staccato bass sound.


Decay describes the amount of time it takes for a sound to go from its peak level to its sustain level. Often, if you hold a note with a particular synth sound selected, you’ll notice the initial ‘impact’ of the sound to be louder than the following sustained volume of the sound. This change in volume might occur quickly, or it might be long and drawn out - this duration is determined by our Decay parameter.


The Sustain parameter, contrary to Attack and Decay, determines level rather than time. It dictates the volume between our Decay and Release phase. For example, if our Sustain is set to maximum, we will not notice a difference in volume from our peak level to our sustain level. This would essentially render the Decay parameter obsolete. However, if we had a lower sustain level, our synth sound would be more dynamic, with a loud punchy impact followed by a softer tail. If we wound down the sustain to zero, we would have a stab/pluck sound - in other words, no tail at all.


Finally, Release is the amount of time it takes for our sound to reach silence once we take our fingers off the keyboard. A long release time can be quite beautiful when creating pad sounds, with each chord flowing into the next. It can also be quite nice on particular lead synth sounds, like in the synthwave genre - for example, the lead line near the end of Kids from the Stranger Things theme.


Here’s a visual representation of the ASDR components we’ve just covered:



The above diagram shows when each of the ADSR components of an envelope occur, and what they control. The “Key pressed” and “Key released” points on the diagram illustrate the role of the Release parameter. Remember, once the key is released, the Release time of the note begins.


Now you have an understanding of ASDR parameters, play around with the master envelope on your favourite synthesizer and see what you can do. There are plenty of free subtractive synthesizers to purchase online if your DAW doesn’t already have one built in. To start, perhaps build a nice pad sound - choose a sawtooth waveform with a long attack, medium decay, high sustain, and medium-to-long release.


Let’s leave it there for now. Keep that pad synth you’ve built handy, we’ll be needing it. Stay tuned for the next instalment of the series where we’ll be discussing LFOs!

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