Caterpillar is a 64-bit stereo enhancement tool by Darkpalace Studio. It is available as AU, LV2, VST3, and CLAP and is completely free.
You might already have a stereoizer and stereo-widener, so what’s the deal with Caterpillar?
In short, the plugin applies bell-shaped peak filters with alternating gain to your audio channels. This results in a broader and potentially deeper stereo image, while preserving mono compatibility.
You can see it in action here:
Going off the rails with stereo imaging is always fun, but listening back in a different environment and figuring out that half your mix is gone and the clarity is destroyed is well… Not great. We’ve all been there.
Using the spread EQ in Caterpillar alleviates most of this problem. Our ears perceive the contrast between left and right channels as more width.
Choosing the number of bell filters, their Q-values, and the frequencies to process gives you more granular control for specific mixing tasks.
Of course, you could create a template with the stock EQs of your choice to recreate the main concept, but there is something enticing about a CPU-effective streamlined workflow that plugins like Caterpillar present. In my experience, it’s less work to set up and way easier to automate.
The plugin also has a correlation meter, visualizer, selectable oversampling, different phase modes, a delta button, and dry/mix control, amongst other things.
What is a relatively uncontroversial spread EQ on the surface is actually a powerful and flexible sound design tool.
Create wild bass or high frequency resonances, formant filter-like effects, and more. Slap some modulation on that thing, combine it with an effect chain of your choice, and see where it takes you!
Used sparingly, Caterpillar could also impart some analog character. Fans of Tokyo Dawn Labs might remember when Vlad Goncharov released his “troll” plugin, T Analog Channel, as proof of concept many years ago.
His intuition was that a lot of the analog warmth and mojo we endlessly talk about stems from random differences in tolerance between the channels.
His plugin, which still works and still is free by the way, applies extremely subtle saturation and randomized spread EQ in the left and right channels.
Combine Caterpillar with a dual mono saturator automated with varying degrees of saturation and see if you can’t get the upper hand on plugin-industry “magic” boxes that cost a fortune. Your wallet and future skills might thank you.
If you want to dive into the details, Caterpillar comes with a nice and comprehensive manual, but this plugin should be easy to tweak right out of the box.
If you are on the lookout for another kind of stereo widener, check out Wider 2 by Polyverse that we’ve covered here at BPB.
To get Caterpillar, you need to register for an account on their website.
Download: Caterpillar (FREE with account registration)
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Last Updated on May 23, 2025 by Tomislav Zlatic.
