5 Rare and Underrated VST Plugins for Mixing
Updated: Sep 25
Five underrated VST plugins that give a mix character instead of polish: Acon Digital Multiply, a free chorus that thickens without the usual phasey smear; Sonic Charge Permut8, a programmable 12-bit delay that sounds like broken 1980s hardware; AudioThing Wires, an old wire recorder in a plugin; HY-Plugins HY-Filter4, a semi-modular filter with a free version; and Klanghelm MJUC jr., a free compressor modelled on early 1960s variable-mu designs. This guide covers what each one does, how we would use it on a band mix, and why the plugins you already own matter more than any of them.
Three of the five have free versions. None of them will fix a song. All of them can give one a bit more personality.
The five at a glance
Acon Digital Multiply (free): a chorus that uses up to six simulated voices with phase randomising, so it widens and thickens without the comb-filter wobble most choruses have. Now on version 2.
Sonic Charge Permut8: a 12-bit digital delay with a variable sample rate and programmable "operators", shipping with around 320 presets from clean echoes to circuit-bent chaos.
AudioThing Wires: a wire recorder emulation, the format before tape, with the noise, wobble and narrow tone that come with it.
HY-Plugins HY-Filter4 (free version available): a semi-modular filter where LFOs, envelope followers and random sources can move almost anything.
Klanghelm MJUC jr. (free): a variable-mu compressor with two gain stages and a transformer stage, capable of smooth levelling or obvious pumping.
Before you download anything: the five processors you already own
A lot of people land on pages like this looking for "the dynamics plugins every mix needs" or "the essential processing tools". The honest answer: every DAW already ships with the five processors that do most of the work in a mix, and they are good enough to make a real record:
EQ, for making space: cutting what fights, not boosting what you wish was there.
Compressor, for controlling level and shaping attack. On band music, less than you think.
De-esser, for taming harsh S sounds on a vocal without dulling the whole voice.
Transient shaper, for adding or softening the attack of drums and guitars.
Limiter, for catching peaks. On a mix bus, usually best left to the mastering stage.
The difference between a flat mix and a great one is almost never which brand of compressor you used. It is what you decided the song needed. Your plugin is rarely the problem, and a pile of bundles won't change that. The five plugins below are here because each one does something your stock plugins cannot, not because they are upgrades.
Acon Digital Multiply: chorus without the seasickness
Most chorus plugins work by copying a signal and wobbling its pitch and timing, which creates the classic shimmer and the classic problem: comb filtering, that hollow, phasey sound that makes guitars feel seasick. Multiply simulates up to six extra voices and runs each through a phase-randomising filter, so it thickens and widens a sound without that hollowness. It also has a built-in EQ and a pre-delay for creating diffuse echoes.
On a band mix we would reach for it on a clean guitar that feels too thin next to a distorted one, or on backing vocals that need to spread out behind the lead. It is free.
Sonic Charge Permut8: the broken machine
Permut8 is built around a 12-bit digital delay whose sample rate you can change, controlled by a small programmable processor. The result sounds like the primitive digital effects units of the 1980s, and then like those units failing. Its presets run from simple delays and flangers to beat repeats, bit crushing and sounds that only exist because something is going wrong.
We would not put it across a whole song. We would put it on one guitar break, a vocal throw at the end of a line, or a drum fill that needs to sound like it fell down the stairs. Used like that, it is one of the most characterful plugins you can own.
AudioThing Wires: before tape
Wire recording came before magnetic tape: sound stored on a thin steel wire, with all the noise, instability and narrow frequency range that implies. Wires recreates that. It makes a sound seem older than anything else in the mix and further away.
Try it on a vocal double placed underneath the lead, on a keyboard part that should feel like a memory, or on the intro of a song before the band comes in. It sits in the same family as the damage plugins in our guide to the weirdest plugins that actually exist.
HY-Plugins HY-Filter4: a filter that moves
A filter is one of the most expressive tools in a mix, and most people only use it as an EQ. HY-Filter4 is semi-modular: a main filter whose settings can be moved by LFOs, an XY pad, envelope followers and random sources. The free version gives you two filter engines and five kinds of modulator, which is plenty.
On band music the useful trick is movement that follows the playing. An envelope follower that opens the filter when the guitarist digs in, or a slow random drift on a synth pad so it never sits still. It sounds alive where a static EQ sounds fixed.
Klanghelm MJUC jr.: a free compressor with a personality
MJUC jr. is modelled on the variable-mu tube compressors of the early 1960s. It has only a few controls, and it can do two very different things: gentle, dense levelling that makes a bass or a vocal feel glued in place, or heavy pumping when you push it. It is free, and it sounds much more expensive than that.
We like it on bass guitar, on a room mic, or across a group of backing vocals. It is also a good teacher, because with so few controls you have to listen to what it is doing rather than read a meter.
Our take: character is a decision, not a download
Every one of these plugins adds character, and every one of them can ruin a mix if it goes on everything. Character plugins work when they are a decision about one part of the song: this guitar should sound older, this vocal should sound further away, this fill should break. They fail when they are used as a way to make a mix sound "interesting" without deciding what the song needs.
That is also why we would rather you learned your stock compressor properly than downloaded five more. The bands we work with who get the best results from plugins like these tend to use very few of them, very deliberately. Why hybrid analogue mixing works for indie music is the longer version of that argument, from the other side of the desk.
What an earlier version of this article got wrong
The plugins in the earlier version were real and still are, so the list stays. The earlier version was very short and did not say what any of them actually does, and it did not mention that three of the five have free versions. This page also now replaces a handful of older posts on this blog about "essential" dynamics and processing plugins, which described generic effect types rather than anything you could actually use.
Underrated plugins FAQ
What are some underrated VST plugins for mixing?
Acon Digital Multiply, Sonic Charge Permut8, AudioThing Wires, HY-Plugins HY-Filter4 and Klanghelm MJUC jr. are five we rate highly. Each adds a specific kind of character that stock plugins do not.
Are there good free mixing plugins?
Yes. Acon Digital Multiply and Klanghelm MJUC jr. are free, and HY-Filter4 has a free version. Your DAW's own EQ, compressor and limiter are also good enough to make a real record.
Which dynamics plugins does a mix actually need?
An EQ, a compressor, a de-esser, a transient shaper and a limiter cover almost everything, and every DAW includes them. How you use them matters far more than which brand you buy.
What is a variable-mu compressor?
A compressor design, originally built with tubes, where the amount of gain reduction changes smoothly with the signal level. It tends to sound gentle and dense, which is why it is popular on buses, bass and vocals.
How do I stop a chorus plugin sounding phasey?
Use less of it, filter the low end out of the chorus signal, or use a plugin like Multiply that randomises phase between voices to avoid comb filtering.
Keep reading
Ready for a mix that uses character on purpose? We mix indie rock, post-punk and shoegaze for artists everywhere, on a hybrid analogue setup, and we would rather make one bold decision than ten safe ones. Send us the rough mix.
