Review: Sonnox Oxford Envolution

Superb plug-in shapes envelopes like no other.
Image placeholder title

There were already several envelope shapers on the market when Oxford Envolution bowed a couple months ago, but none offer the degree of control Sonnox’s Darwinian disrupter brings to the family tree. Rather than merely boost or cut the level of transients and sustain in a signal, Oxford Envolution also lets you independently adjust the attack, hold, and release times for level changes to both portions of the signal’s envelope: Level and time control! Offering frequency-dependent processing and harmonic saturation to boot, Envolution is a whole new envelope-warping species.

The cross-platform Envolution is available in AU, AAX (Native and DSP), and VST formats. I tested V1.0 of the AU plug-in in Digital Performer 9.02, using an 8-core Mac Pro running OS X 10.9.5.


Envolution’s Transients and Sustain controls respectively adjust the level of transients and sustain for the plug-in’s input signals; rotate each control clockwise to boost level up to 24 dB, or drag counterclockwise to cut up to the same amount. Controls for adjusting the attack, hold, and release times—three controls each for transients and sustain—are scaled in percent of their available range rather than in milliseconds (see Figure 1), as their absolute values change depending on the input signal. Lower the Sensitivity control (provided for transients only) to exclude quieter transients from processing.

Fig. 1. Oxford Envolution provides separate controls for adjusting the level and time constants for transient and sustain envelopes. Here, the central display shows the scrolling envelope scope. The Transient Attack, Hold, and Release controls can have a big effect on percussives. Use a slow attack time to allow the leading edge of the transient to pass through the plug-in unchanged, and a fast attack to boost or cut the transient’s level quicker. The Transient Hold control delays the onset of the release portion of the processing; raise it to add low-frequency punch or to prevent the gain envelope for a rapid-fire acoustic guitar performance, for example, from whipsawing up and down on each plucked note. Raising the Transient Release control extends the duration of the transient, providing a smooth decay.

Image placeholder title

The Sustain Attack, Hold, and Release controls work somewhat differently from the same-named controls for transients. Raising the Sustain Hold control delays the onset of the sustain envelope’s attack—not the sustain decay, as you might expect—so that only the tail of the sustain envelope will be boosted or cut. Boosting the Sustain Attack control delays the attainment of maximal sustain boost or cut (set by the Sustain control in dB), although it immediately begins to make the gain adjustment. The Sustain Release control affects how quickly the sustain envelope returns to unity gain when a subsequent transient occurs and is detected.

Fig. 2. Separate, adjustable filters for the transient and sustain envelopes affect both their detection and the frequencies that are processed for each. A broad notch filter for the sustain envelope is shown here. The well-designed GUI’s centrally located display can be switched—using three buttons—to alternately show an envelope scope or separate filters for the transient and sustain envelopes (see Figures 1 and 2). The envelope scope plots amplitude (vertical axis) vs. time (horizontal axis) for three elements at once: the input signal (colored gray), processed transient envelope (yellow), and processed sustain envelope (purple). The scope scrolls by default—at user-selectable slow, medium, or fast speed—but can alternatively be synched to your project to display one-or twobar segments at a time. Click anywhere inside the scope to freeze the display for lingering inspection; a second click unfreezes it.

Image placeholder title

Envolution’s filters affect both the detection and processing of envelopes, letting you vary the strength of processing for transient and sustain envelopes at different frequencies; the filters don’t split the audio into separate frequency bands, which would cause subtle phase issues. For each envelope—transient and sustain—you can select a different type of filter: tilt, highpass, lowpass, bandpass, or notch. Each filter offers three parameter controls to fine-tune their shape, and the central display plots the resulting wet-dry balance (along the y-axis) vs. frequency (x-axis). For example, frequencies in your audio input that are way below the corner frequency for a highpass filter would be 100 percent dry (completely unprocessed).

As you raise Envolution’s Warmth control, harmonic saturation is added at the plug-in’s output (to a degree not dependent on signal level). When raised sufficiently, the Warmth control also prevents signal peaks up to +6 dBFS from clipping. This lets you boost transients quite a bit without forcing you to lower the plug-in’s output gain to avoid clipping, thereby preserving sustain levels.

A Mix control adjusts the wet-dry balance, providing both parallel processing and a de facto master control for all the Transient and Sustain controls. Activating Envolution’s Diff button lets you hear only the difference signal (that is, what signal is added to or taken away from the original signal, excluding Warmth processing); it’s useful to hear the difference signal while fine-tuning the Transient Sensitivity control to prevent unwanted transients from being processed. Rounding out the GUI are separate envelope bypasses, output-level fader and meter, informative Help balloons, flexible A and B banks (copy from and paste to any instance of the plug-in!), 16 levels of Undo and Redo, and proprietary preset-management facilities (affording portability between DAWs).


Envolution shapes drum sounds like no other envelope shaper can. As expected, boosting the Transients control and using a fast attack enhanced stick strikes on snare drum. The real magic began when I raised the Transient Hold and Release controls roughly halfway to max and jacked up the Warmth control. This greatly enhanced the sizzle of the snares. In fact, I often found myself setting the Transient Hold time between the 11 o’clock and noon positions when boosting the attack of other trap drums, as doing so thickened the attack in a way not achievable by applying EQ; it made the drummer sound like he was using bigger sticks! Using the lowest possible Sensitivity setting kept enhancement of hi-hat bleed on the track to a minimum (although I wished this control was even more discriminating).

Turning my attention to the snare drum’s sustain, I boosted the Sustain and Sustain Hold controls to increase the audibility of the shell’s decay following batter-head strikes. Processing the sustain envelope with a 294Hz notch filter tamed the unwanted sound of the shell ringing at a fundamental pitch of D natural. The combined result of all my tweaks sounded perhaps a little over the top, so I reduced the Mix control to 92 percent to add back some dry signal. The snare drum sounded incredible.

I also got awesome results using Envolution on a floor tom playing half notes. Boosting transients—using similar time constants as I did previously for snare drum—and shaping Envolution’s transient filter for a peak at 200 Hz made the stick hits sound not just louder but beefier. To make the drum’s shell thunder, I goosed the Sustain control and fashioned a lowpass filter with a 156Hz corner frequency for the sustain envelope. Cranking the Sustain Release control to the max did two things: It prevented the thunderous sustain from being cut short on each subsequent stick hit, and it added low-bass boost to overlapping transients by applying the sustain envelope’s processing to them. Raising Envolution’s Sustain Hold control a little bit separated in time the processed sustain envelope ever so slightly from transient stick hits, reducing masking and making the thundering shell resonance sound more distinct. The end result sounded absolutely phenomenal and transformative.

Envolution also sounded outstanding on female lead vocals. The unprocessed vocal sounded very slightly thin and lacked immediacy. I fashioned a narrow peaking filter for the transient envelope, centered at 1.74 kHz—low enough so as not to augment sibilance. Raising the Transients control around 4.5 dB and lowering all time constants for the transient envelope to their fastest values, the singer sounded like she stepped several inches closer to the mic. Cool! Next, I fashioned a narrow bandpass filter for the sustain envelope, centered at 204 Hz, to reinforce the singer’s chest register. Adding around 7 dB of Sustain and setting the Sustain Hold, Attack, and Release controls to around 10 o’clock made her sound more powerful without causing any boominess or veiling her consonants. Raising the Warmth control halfway added a little extra size and luster to the track. The end result was a spectrally balanced, stronger, and more articulate and compelling money track.

I observed only two minor bugs. More important, Envolution lacks an external sidechain input, a feature the competing SPL Transient Designer Plus can use to make other tracks trigger its wideband processing. Even so, Envolution shapes envelopes like no other product can. Uniquely powerful, flexible, and reasonably priced, Oxford Envolution is a terrific-sounding plug-in every mix engineer should own.


Best of breed. Sounds phenomenal. Adjustable time constants. Frequency-dependent processing, with flexible filters. Includes flattering harmonic saturation. Very welldesigned GUI. Reasonable price.


No external sidechain input. Sensitivity control could have a slightly wider range. A couple minor bugs.

Native: $270
Pro Tools HDX: $435

Michael Cooper is a recording, mix, mastering, and post-production engineer and a contributing editor for Mix magazine. You can reach Michael at and hear some of his mixes at