Synth Envelopes – Case Studies: Korg Wavestation

I promised you a case study on the Korg Wavestation’s envelopes. That was three years ago. Now, I’m finally going to follow up on that promise.

Note that I won’t repeat all the details about the test case definition from the last post – so better read them up there.

The Wavestation Envelopes

The Wavestation (or in our case, both the Wavestation KEX and the Legacy Edition plugin version) are true to what I’d like to call the second generation of digital synths.

At this point, Moore’s Law had started to give synth designers so much computing power that they started to think outside of the box of 70s analogue synth design. And one area where improvements were made were the envelopes. Like many of its contemporaries, the Wavestation has more than just the usual four-parameter four-stage ADSRs.

While the envelopes look at first sight like normal four-stage envelopes, the tricky part is that every stage has parameters for time and level. Level, in this case, is level at that stage’s start (although Korg has named the parameters differently by having levels for segments 0-3 and times for segments 1-4). As usual, the first stage is triggered by gate on, and stage 3 is the sustain stage, i.e. where it will reside until the key is released?

However, this eight-parameter-setup allows for some tricky things impossible with the usual envelopes. As the sustain portion also has a time, you can think of it as a second decay stage. And as the attack portion has a level (as has the decay portion), you can also have a two-part attack and one-part decay. Finally, by setting the “level 0” to nonzero values, you can use that as a super-snappy first part of the attack portion. A lot is possible – sadly with the exception of having a divided release stage.

Test Setup

To simplify things, I opted to start for some qualitative comparisons between the KEX hardware and the plugin version. Finding a proper much between both (which is in line with most findings from the community), I opted to simplify the process by using the plugin version, thus getting rid of potential artifacts caused by MIDI or audio interfaces.

Furthermore, differently from last time, I used a square wave for the setup for all test cases.

Now, on to the test cases.

Curve Shape


A clear statement: the envelope is linear.


For the shortest setting for attack and decay, it looks like this:


If you zoom in further on the attack portion, you find that it takes about eight samples to reach full level. Considering the 48kHz sample rate, this ends up as ca. 167us, i.e. considerably below 1ms.

What’s more interesting here is the decay portion, which also at its minimum setting takes about 15ms – about 100 times longer.

For the longest setting, the picture looks like this:


Thirty-seven seconds is a statement. Then again, the Wavestation mostly excels at ambient-ish pad sounds, so this doesn’t come as a surprise after all.

State Machine – Gate off during Decay


Again, a pretty clear picture: If a gate off happens during decay, the envelope immediately jumps to the release section.

State Machine – Gate on during Release


Also a pretty clear situation: if we receive a gate on during release, the level jumps to zero (or rather most probably the “initial” value) and then starts the attack phase.

There is a question if the release portion seen here can be called truly linear – maybe not. This is in contrast to the decay section we’ve clearly seen in the Duration use case above as being spot-on linear.

State Machine – Gate on during Sustain

I don’t know if there is a kind of mono-synth mode for this, but I haven’t found it, making this test impossible to execute.


It’s nice to see that clear transition for the Gate on during Release case. Apart from that, as the Duration measurements show, the envelopes do go from super-snappy sub-ms to more than half a second – good for anything.

A state machine, as far as it can be described from the manual and these measurements alone, would look like this:

Wavestation Envelope.png

I consider the Wavestation’s envelopes some truly evolved envelopes: while they don’t move away from the concepts we’ve known ever since the dawn of synth, they add the simple but important detail of having both level and duration parameters for each of the four stages – and with that, allow for truly complex envelope patterns.


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