Vintage polysynth emulations are everywhere, but few let you play them the way their original builders could never have imagined. Cherry Audio's Mercury-4 is a modeled take on a classic four-voice analog poly that adds comprehensive MPE support, turning a 1970s sound into an instrument that responds to per-note pressure, slide and pitch.
What Mercury-4 offers
The original hardware it is inspired by had only four voices. Mercury-4 expands that to 16-voice polyphony, which matters a great deal once you start playing full, overlapping chords with an expressive controller. Each note needs its own voice to carry its own gesture data, and running out of voices mid-phrase is a quick way to ruin a performance.
Other headline features include:
- A modeled oscillator with a sub oscillator and dual filters with low-frequency resonance modeling
- Over 400 presets, including the original factory sounds
- A tempo-synced arpeggiator, a stereo ensemble effect, and a tape echo with reverb modes
- A drift control for analog-style instability
- A single-key chord memory mode and a detunable unison mode
- User-adjustable oversampling for cleaner high-frequency behavior
According to the KVR Audio product listing, the current version is 1.6.0. Version 1.5 introduced a better preset browser with single-click favoriting, preset-level MIDI mappings, and zip-based preset library imports.
Why MPE suits a vintage poly
Classic analog polysynths are often considered pad and chord machines, but their simple, immediate controls pair surprisingly well with MPE. Mapping slide to filter cutoff gives each finger its own filter sweep. Mapping pressure to volume or vibrato lets sustained pad notes swell individually. The drift control adds a subtle instability that blends well with the natural movement of a human hand.
The result is that a single chord can have a bright note on top, a darker note in the middle and a gently wavering bass, all from the same patch.
Formats and price
Mercury-4 costs $49 and ships as VST, VST3, Audio Unit and AAX plugins, plus a standalone application. It supports macOS 10.9 and later, including Apple Silicon, and Windows 7 or later in 64-bit. A 30-day demo is available, which includes periodic white noise, so you can try it with your own controller before buying.
Who should consider it
If you own an MPE controller and want a warm, characterful poly rather than a wavetable or modular engine, Mercury-4 is a budget-friendly option. Owners of an Osmose, Seaboard or LinnStrument will get the most from it, though players with standard keyboards can still use it as a straightforward vintage synth.
A practical tip: if your controller's default pitch bend range does not match the plugin's, notes can sound out of tune during glides. Check the MPE settings in both your DAW and the instrument before recording. You can find more setup guides on the mpesynth.com blog.