Diagram of an ADSR envelope from the original ARP2600 manual

×

It's important to realize that Sustain is not a stage measured in time; it's a level that remains for as long as the Gate is held open, like when holding down a key on a keyboard synth. If the Sustain is set to the maximum, then there will be no Decay, as it has nowhere to go. Alternatively, if it's set to zero, then the envelope is simply the length of the Attack and Decay. In fact, there tend to be a lot of Attack/Decay envelopes in modular. These are often called Rise and Fall which really helps visualize what’s going on. They are great for fast-moving basslines or short blips and beeps that are common in electronic music. Or, as you increase the Rise and Fall times, they can offer dramatic changes in direction and intentional modulation. A whole four-stage ADSR envelope can feel a bit redundant in a modular system without a keyboard, and so often an AD or Rise/Fall will be plenty.

Finally, we have Release, which is what happens to the voltage once the key is released or Gate is closed. What we hear, the dissipation of sound, is often what we would call “sustain”, like holding the Sustain pedal on a piano. In synthesis, Sustain is a held sound, whereas Release is the sound reducing to zero once you've stopped playing. It’s easy to get those terms confused.

Let's begin with the most basic example of the ADSR envelope, which, of course, comes from Doepfer. The A-140-2 features two identical envelopes with knob controls to set the timing of Attack, Decay, and Release, as well as the level for Sustain. A Gate input starts the envelope on its journey, and a red LED shows the intensity along the path. A retrigger input interrupts the envelope cycle and fires it again from the beginning.

There's an attenuable CV input that can be configured via jumpers on the back to provide external voltage control over either the length of the Decay, Decay and Release, or the whole lot. The two outputs are useful for sending the same envelope to a VCA and a filter cutoff. Alternatively, you can set one output to be inverted so it pulls the voltage down rather than pushing it up.

It's effortless and effective.

The Soundforce Dual ADSR keeps it simple but gravitates towards a slider approach, as found on and inspired by the Roland Juno 106. I find that sliders can often better visualize the envelope, as they give an impression of the shape from left to right to some degree, while the red LED lends additional support in tracking the envelope's shape over time. The sliders aren't strictly labelled, but there's no doubt as to what they control.

With this module, we have individual CV control over each stage, which can produce massive variations in the shape and length of the envelope. But we also have a bunch of other controls. You can switch between short, medium, and long time ranges, going from super-snappy to up to 60 seconds. You can also choose to have the shape of the Attack, Decay, and Release follow a linear path or an exponential curve, the latter of which can sound more natural when controlling volume. A flick of a switch will send the envelope into a cycling mode, turning it into a shaped LFO.

In terms of connections, we have Gate and Retrigger, as well as both fixed and inverted outputs. Finally, an End-Of-Cycle output sends a gate whenever a stage of the envelope has finished. This can be set to fire at the end of any stage of your choice.

Tangrams is a good, clear, slider-based twin ADSR with some funky functions dotted around the front panel that give it a huge amount of versatility. For basic envelope usage, you have three speed ranges, retriggering, and some useful manual trigger buttons to fire off the envelope to order. Then it starts to get interesting.

Intellijel has included a "Pulser" function which can use a trigger to fire the envelope, which then acts like a gated envelope by setting Gate on/off times. T1 sets how long the Gate is held on, and then T2 sets how long the gap is before the next Gate. When used together with both envelopes, you can create offsets and delays between the triggering which can get very interesting, especially when they are cycling. There's even a handy Start button to control the motion of the Pulsar sequence. It's inspired by the trapezoidal function generators found on the EMI Synthi, but for us, it can enable some very interesting gate patterns.

The other useful feature is the inclusion of VCAs. Normally, an envelope would be used to shape the output of a separate VCA module. Conveniently, Tangrams features VCAs onboard so you can use it to control the amplitude of another signal without having to use a separate VCA. Simply plug your signal into the VCA input, and it will be shaped by the envelope. Some people would call that cheating!

If you find the shapes of regular envelopes to be a bit unimaginative, then perhaps you should browse the 260 envelope shapes found in the Zadar. Where other envelopes are set by intuitive feel and rough knob position, Zadar is all about precision, giving you the exact shape you're after.

The idea is that you can create a function built from 1000 segments that can be warped, reversed, and stretched. The time it takes to move through the function can vary from 0.85ms to half an hour. You can modulate any assignable parameter, you can loop envelopes to create LFOs, and even chain different envelopes together. Zadar has four identical channels of this.

It sounds like the sort of thing that would be impossible to achieve with a module that has only a couple of knobs and an OLED display. However, the reality is that you begin with one of the shapes and can then quickly push into the different elements to fashion it into exactly what you need. The preset shapes cover all sorts of eventualities, from familiar envelopes to LFO waveforms through to transients, complex voltage equations, patterns and much much more. You then take the Warp knob to deform the shape in different directions. Another knob handles the function's time, while another attenuates the level.

As a starting point, you have a simple Attack/Decay envelope and a trigger input. However, if you use the Gate input, you can expand the envelope by pushing Attack and Decay apart for as long as the Gate is open. This might be called an Attack - Hold - Release envelope in some circles, but I think you can understand what's going on intuitively, jargon aside. At the end of the envelope, Pip Slope sends out a trigger to cascade into something useful in your rack.

A shape control can warp the lines of modulation from exponential to logarithmic, with CV control over both the Attack and Decay for lots of variation. However, it's the Loop control that adds a touch of specialness to this module. There are three Loop modes. The first acts like a regular LFO by looping the entire envelope, where the Attack and Decay control the envelope shape and alter its speed by shortening or lengthening the loop. Another mode cuts the loop time in half with every repeat, creating a sort of increasing echo. The final mode does something similar but with a ratio of 2/3rds, creating a bouncing ball effect. These are the sort of modulations you didn't know you needed until you tried them out.

NANO Modules QUART

This is stunningly simple and quite possibly the envelope you'll use the most in any situation that doesn't require complexity. Quart has four channels of AD envelopes with three speed ranges.

You've got knob control over Rise and Fall times for each channel, all alongside a trigger input and an envelope output. It's dead easy and very effective.

If you leave a channel unpatched, then it will automatically loop itself into an LFO based on the Attack and Decay times.

It's an easy modulator, with useful Rise and Fall envelopes, and no surprises.

The Quadrax may look complicated, but it's really not unlike the Quart. You've got four channels of Rise and Fall envelopes, with knobs, trigger input, envelope output, and all the simplicity of quick functions and intuitive controls. However, there appears to be lots going on in the middle section, and that's going to offer us a whole load of flexibility.

The Shape control in the middle can push the curves from exponential through to logarithmic. The four CV inputs can be assigned to any parameter on any channel, allowing you to have them all modulate different elements of the same channel if you so wish. However, Quadrax has a bunch of other modes. You can extend it into a gated Attack, Sustain, Release envelope, you can cycle them into both unipolar and bipolar LFOs, and you can get them to "pulse burst" a bit like the Tangrams. You can even sync all the channels together using divisions and multiplications for combined effectiveness.

Quadrax has a lot going on under those buttons that can take its basic functions off into some excellent directions.

Polyphony is not considered an easy thing in modular. It often requires multiple modules to handle different voices and a level of complexity to manage note allocation and response. However, multi-channel envelope modules and other modules with multiple channels can quickly start to pull a polyphonic patch together when used in combination. The Verbos Polyphonic Envelope definitely leans into the merits of working together.

All four envelopes in this module are linked to the central Attack, Hold, and Decay sliders. You then have four gate inputs and CV outputs to enable you to use the four envelopes independently. However, it's much more fun to use them together. Through various modes, you can trigger the envelopes sequentially, creating chains of envelopes for working on elements of a single voice or for giving the impression of arpeggiation across multiple voices. The envelopes can be pushed further apart using the slew controls, which adjust their respective amplitudes or relationships.

The Polyphonic Envelope is an elegant and creative way of managing modulation in complex patches and multi-voice systems.