# Dexed: Free DX7 FM Synthesizer Plugin for VST3, AU, CLAP, and Standalone

> Dexed is a free, GPL-licensed FM synthesizer plugin closely modeled on the Yamaha DX7, available for Windows, macOS, and Linux as VST3, AU, CLAP formats and a standalone application. It uses Google's music-synthesizer-for-android engine for accurate DX7 emulation, includes a Cartridge Manager for loading sysex patch collections, and adds microtuning and MPE support that the original DX7 hardware lacked.

**asb2m10/dexed** — DX7 FM multi plaform/multi format plugin

- Repository: https://github.com/asb2m10/dexed
- Stars: 3,545 · Forks: 303
- Language: C++
- License: GPL-3.0
- Published: 2026-09-23 · Updated: 2026-09-23 · Language: en
- Canonical page: https://hysenlabs.com/projects/asb2m10-dexed

## A DX7 Emulator for Modern Plugin Hosts

The Yamaha DX7, introduced in 1983, used frequency modulation (FM) synthesis to produce its characteristic electric piano, bass, and bell tones. FM synthesis generates sound by modulating the frequency of one oscillator (a carrier) with another (a modulator), producing complex harmonics from simple sine waves. The DX7 had six operators arranged in 32 fixed algorithm configurations.

Dexed models this architecture precisely. The README states its goal as a companion tool for the original DX7, with a synth engine that preserves the original's behavior. Anything that goes beyond what the DX7 can do, the README says, should be a fork rather than a modification to Dexed. This commitment to compatibility means that every patch designed for the original DX7 should sound correct in Dexed, and DX7 sysex messages can be sent to and from both the plugin and the original hardware.

Dexed targets music producers and audio engineers who want DX7 sounds in a plugin format compatible with modern DAWs, as well as researchers and developers interested in FM synthesis who want a well-documented open-source implementation.

## The MSFA Engine and JUCE Framework

Under the hood, Dexed combines two open-source components. The synthesis engine is msfa (music-synthesizer-for-android), originally developed by Raph Levien and the msfa team at Google. This component is licensed separately under Apache 2.0, which allows it to be reused in other projects without the GPL restrictions that apply to the rest of Dexed. The msfa engine handles the actual FM operator calculations, envelope generators, and LFO behavior.

JUCE wraps the engine as an application and plugin. JUCE is a C++ framework for audio plugins that generates VST3, AU, CLAP, and standalone builds from a single codebase. This is why Dexed runs on Windows, macOS, and Linux across multiple plugin formats without requiring separate codebases for each.

The Mark I engine is the default and most accurate DX7 emulation. It uses 10-bit sine and exponential tables to match the original hardware's behavior. The README notes that feedback implementation for algorithms 4 and 6 was specifically calibrated for the Mark I engine. An OPL Series engine is also included for a different FM character.

## Installing Dexed: Prebuilt Packages, Nightly Builds, and Stable Releases

The README directs users to the Dexed User Website for download and installation information. Prebuilt installers for Windows and macOS have been available since version 0.9.4, which added Windows and macOS installer support. macOS releases have been notarized since version 0.9.7.

For developers who want to build from source, clone the repository with its submodules:

```
~ $ git clone https://github.com/asb2m10/dexed.git
```

The README notes the repository has several submodules it depends on. CMake has been the build system since version 0.9.7. The repository includes a JUCE submodule.

Nightly prerelease builds are available through GitHub Releases under the Nightly tag. Version 1.0.1 is the most recent stable release (2025-11-29), with the Nightly tag updated on 2026-07-21. The last push to the repository was on 2026-09-21.

## Sysex Compatibility and the Cartridge Manager

DX7 patches are stored as sysex (system exclusive MIDI) messages. A full bank of 32 voices is 4104 bytes; individual patches are smaller. Dexed accepts sysex files in 4104 or 4096 byte sizes, and the README says the validation is based on size rather than strict type checking, making it more permissive with real-world sysex files from the 1980s.

The Cartridge Manager, added in version 0.9.0, provides a browser for loading and managing patch collections. Version 0.9.1 added the ability to drag and drop `.syx` files directly into the Cartridge Manager, and to send the current program to a connected DX7 hardware unit. Version 0.9.2 improved single-click program selection.

Version 0.9.3 added support for sysex streams, meaning a single `.syx` file can contain multiple sysex messages, which is common in collected patch archives. Dexed also replies to sysex Patch Request messages, as added in version 0.9.9, making it respond to the same MIDI commands a hardware DX7 would.

## Microtuning, MPE, and Accessibility

Dexed has moved beyond strict DX7 replication in a few areas where the additions remain compatible with the original's core architecture. Version 0.9.5 added SCL/KBM microtuning support, which lets users load Scala tuning files for alternative pitch systems. Version 0.9.7 added MTS-ESP (MIDI Tuning Standard, Exposed Protocol) support, enabling real-time microtuning from a compatible tuning manager application. The Surge Synth Team contributed both the microtuning and MPE support, according to the README credits.

MPE (MIDI Polyphonic Expression), also added in 0.9.5, allows per-note control of pitch, pressure, and slide on MPE-compatible controllers. Version 0.9.8 added a full accessibility implementation including keyboard shortcuts, documented in a separate `Documentation/Keybindings.md` file. The Mono/Poly parameter became a plugin parameter in the same release, meaning DAWs can automate between monophonic and polyphonic modes.

Version 1.0.1 changed how DAW UI scaling and user zoom interact: the DAW scales the UI first, and the user can zoom further from there. Plugin parameter dialogs moved into the main plugin window in the same release, removing the separate floating windows that previous versions used.

## License Split, Project Boundary, and Build Constraints

Dexed is licensed under GPL v3. The msfa synth engine component, under the `msfa` directory in the source, retains its Apache 2.0 license. The README explicitly notes this split to allow collaboration between projects. GPL v3 requires that any software derived from Dexed and distributed must also be published under GPL v3 with its source code. The msfa component can be reused under Apache 2.0 without that requirement.

The project has a declared scope boundary. The README states that any feature going beyond the DX7 should be a fork, not a modification to Dexed. Two listed forks extend the project: MiniDexed runs a DX7 emulation directly on Raspberry Pi hardware without a DAW, and a SIMD-optimized fork uses Google's highway library for CPU-accelerated DSP.

The build system uses CMake since version 0.9.7. The repository includes submodules, which must be initialized after cloning. The README does not provide step-by-step build instructions in its main text; it refers to the user website for that information. macOS users who cannot build from source should use the notarized prebuilt installer to avoid Gatekeeper warnings.

## Dexed Compared to General-Purpose FM Synthesizers

Dexed's defining characteristic compared to other free FM synthesizers is its strict 6-operator DX7 compatibility and sysex import. ZynAddSubFX is a free and open-source synthesizer that combines additive, subtractive, and FM synthesis with a much larger operator count and its own patch format. It targets more general synthesis rather than faithful emulation of a specific vintage instrument. The trade-off is that ZynAddSubFX patches are not interchangeable with DX7 sysex, and its interface is more complex.

For producers who own DX7 sysex cartridge archives or want to exchange patches with original DX7 hardware, Dexed's emulation accuracy and sysex compatibility are the key differentiators. Engineers who want a broader FM palette, arbitrary operator counts, or synthesis approaches beyond pure FM will find Dexed's self-imposed DX7 boundary limiting.

The TODO list in the README notes two items still outstanding: code cleanup and Yamaha 4-operator DX21/DX27/DX100 sysex import. The 4-operator import has been on the list for multiple versions and remains unimplemented.

## Conclusion

Dexed is a good fit for producers and engineers who want accurate DX7 FM synthesis in a modern plugin host without acquiring vintage hardware. Existing DX7 sysex patch libraries load directly, and MTS-ESP and SCL/KBM microtuning support extends the hardware's capabilities. The GPL v3 license requires derivative works to be open source, so commercial forks must comply; the msfa synth engine component remains Apache 2.0 and can be used more freely. The stated project boundary is DX7 compatibility: features that go beyond the DX7 should fork the project rather than modify Dexed. Building from source requires CMake and has Git submodule dependencies. Prebuilt installers are available at the project's user website for those who do not need to compile from source.

## FAQ

### Is Dexed VST free?

Yes. Dexed is released under the GPL v3 license. The README directs users to the Dexed User Website for download and installation. Prebuilt installers for Windows and macOS are available there at no cost.

### Is Dexed a good synth?

The README describes Dexed as closely modeled on the Yamaha DX7 and states its goal as DX7 compatibility. Its Mark I engine uses 10-bit sine and exponential tables to match the original hardware's sound. It accepts real DX7 sysex files and can send patches back to hardware DX7 units.

### How do I install Dexed?

The README directs users to the Dexed User Website (asb2m10.github.io/dexed) for download and installation information. Prebuilt installers for Windows and macOS have been available since version 0.9.4. macOS releases have been notarized since version 0.9.7. Nightly builds are available on the GitHub Releases page.

### What does "dexed" mean?

The README does not explain the name directly. The name appears to be a play on "DX", referring to the Yamaha DX7, the FM synthesizer that Dexed emulates.

## Sources

- [asb2m10/dexed on GitHub](https://github.com/asb2m10/dexed)
- [Issues](https://github.com/asb2m10/dexed/issues)
- [License: GPL-3.0](https://github.com/asb2m10/dexed/blob/master/LICENSE)
- [README](https://github.com/asb2m10/dexed/blob/master/README.md)
- [Releases](https://github.com/asb2m10/dexed/releases)

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Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/asb2m10-dexed