RDX opens .syx voice cartridges from classic 6-operator FM synthesizers, plays every voice through a built-in FM engine, and lets you rename, reorder, merge and export new banks — all on your device. It now also runs as an AUv3 plug-in in your DAW.
Features
Preview, instantly
Play any voice through a faithful 6-operator FM engine — on-screen keys, computer keys or MIDI in.
Rename & reorder
Edit voice names inline and drag to organize your bank exactly how you want it.
Merge & build
Cherry-pick voices across many cartridges and export a fresh bank.
AUv3 plug-in
Play RDX as an AUv3 instrument inside AUM, GarageBand, Logic and other hosts.
Per-voice volume & pan
In the Play tab, set each voice's volume (in dB) and balance.
32 or 64 voices
Export single 32-voice cartridges or 64-voice (two-bank) files — split with no loss.
Pitch & mod wheels
Expressive preview with bend and modulation wheels, plus full MIDI device selection.
No accounts, no cloud
Your files never leave the device. Nothing is uploaded, ever.
What it's for
RDX is a voice-bank librarian for 6-operator FM synthesizers. It opens .syx cartridges (sysex messages) of 32 and 64 voices, plays each patch through a faithful FM engine — with an on-screen keyboard, computer keyboard or MIDI — and lets you rename, reorder, merge voices from many cartridges and export new banks (32 or 64 voices, split with no loss). Perfect for collecting and organizing classic FM patches on iPhone, iPad and Mac. Beyond standalone, RDX runs as an AUv3 plug-in (instrument) in your DAW and splits organizing (Library tab) from playing (Play tab, with per-voice volume and pan).
See it in action
Screens
Controls
Toolbar
| Control | What it does | Range / options |
|---|---|---|
| Open .syx | Load voice cartridges (32 or 64 voices) | multiple files |
| Export | Save the selected voices as a new .syx cartridge | — |
| Select all | Toggle every voice on/off | on/off |
| Group selected | Move the checked voices to the top of the list | — |
| Clear | Empty the library | — |
| Settings | Export format, audio and MIDI | — |
Voice list
| Control | What it does | Range / options |
|---|---|---|
| Select voice | Mark the voice for export | on/off |
| Play / preview | Tap a voice to hear it through the 6-operator FM engine | — |
| Rename | Tap the name and edit it (written into the exported cartridge) | up to 10 chars |
| Algorithm | The voice's FM algorithm number (read-only) | 1 … 32 |
| Reorder (drag) | Hold and drag to reorder | — |
Player & MIDI
| Control | What it does | Range / options |
|---|---|---|
| On-screen keyboard | Play the voices; the vertical touch position sets the intensity (velocity) | ~2.5 octaves |
| Octave (▲ ▼) | Shift the keyboard by an octave | C−1 … C8 |
| Per-voice volume | Each voice's volume in the Play tab (double-tap to reset) | −60 … +6 dB |
| Per-voice pan | Each voice's stereo balance | L … C … R |
| Pitch bend | Wheel that springs back to center on release | ±2 semitones |
| Modulation | Wheel that stays where you leave it | 0 … 127 |
| Format (in Settings) | Cartridge size on export | 32 (1 bank) · 64 (2 banks) |
FAQ
What is a .syx (sysex) file?
It is a MIDI SysEx (System Exclusive) dump that stores a synth's voices/patches. RDX reads these .syx cartridges from 6-operator FM synthesizers.
Does RDX play the voices or just list them?
It plays them. There is a built-in 6-operator FM engine — play any voice with the on-screen keyboard, your computer keyboard or a MIDI controller.
Can I merge voices from several cartridges?
Yes. Pick voices from as many cartridges as you want and export a new 32- or 64-voice bank.
Can I rename and reorder voices?
Yes — edit each voice name and drag to organize the bank before exporting.
Which devices does RDX run on?
iPhone, iPad and Mac — now on the App Store.
Does RDX work as an AUv3 plug-in?
Yes. Besides standalone, it runs as an AUv3 instrument inside hosts like AUM, GarageBand and Logic. One Mac detail that confuses people: in the AUv3 format the plug-in lives INSIDE the app, so there is no file to copy into Components or VST — just open RDX once and it shows up in your software's list as "RSJB: RDX FM".
Which synths is it compatible with?
Classic 6-operator FM synthesizers that use .syx voice cartridges. RDX is an independent product, not affiliated with any manufacturer.
A cartridge is in iCloud and won't open. What do I do?
Nothing — RDX handles it on its own. When you pick a .syx that lives only in the cloud, it asks for the download, shows you the wait and loads the cartridge as soon as the file lands. Before, choosing it just failed silently.