EMETERIO
V20
A complete browser-based editor for the Roland MT-32 Multi-Timbral Sound Module. Edit timbres, manage your library, configure performance and rhythm — all via Web MIDI, no software required.
Requirements
- Browser: Google Chrome or Microsoft Edge (Web MIDI API required). Firefox and Safari are not supported.
- MIDI interface: A USB-MIDI interface that supports SysEx, or a USB cable if your MT-32 has USB-MIDI.
- MT-32 settings: SysEx must be enabled on your unit. Check your MT-32 manual under System settings.
- HTTPS: The editor must be served from a secure (https://) URL for Web MIDI to work. Running from a local file:// URL will not work.
The first time you open the editor, Chrome will ask for MIDI access permission. Click Allow — without this the editor cannot communicate with your hardware.
MIDI Connection
- Connect your MT-32 to your computer via a USB-MIDI interface. Make sure MIDI IN and MIDI OUT are both connected.
- Open the editor in Chrome or Edge.
- Grant MIDI access when prompted by the browser.
- In the top bar, select your MIDI input and output ports from the dropdowns. Both should point to your interface.
- Click the ⟳ refresh button if your device doesn't appear — plug it in before opening the editor.
- The status indicator in the top right will turn green when the connection is active.
Make sure no other software (DAW, etc.) is using the same MIDI ports simultaneously. Shared MIDI access can cause dropped SysEx messages.
Interface Overview
The editor is organized into five main sections, accessible via the tab bar at the top:
| Tab | Description |
|---|---|
| 📦 Library | Manage your master library of timbres. Import .syx files, organize into folders, search and transfer timbres to the editor slots. |
| ✏️ Timbre Editor | Edit the 64 user timbre slots. Full LA synthesis control with partial editor, WG, TVF, TVA, envelopes and more. |
| 🎹 Performance | Configure MIDI channels, volume and other performance settings for each of the 8 parts. |
| ⚙ System | Global MT-32 settings: master volume, reverb mode, and system parameters. |
| 🥁 Rhythm | Configure the rhythm part: assign PCM samples to rhythm keys, set level, output and reverb per key. |
The right-hand side panel handles MIDI transmission — sending your edits to the MT-32, loading .syx files, and saving your work.
📦 Library
The Library is your master collection of timbres — separate from the 64 editable slots. You can store hundreds of timbres here, organized into folders, and transfer them to the edit slots as needed.
Loading timbres into the Library
- Click 📂 Cargar .syx → Biblioteca to import a SysEx file directly into the library. Timbres are added to the current folder.
- Click 📂 Abrir .json to load a previously saved library in JSON format (includes folder structure and names).
Organizing with folders
- Click 📁 + Carpeta to create a new folder.
- Click the pencil icon ✎ next to a folder name to rename it.
- Click the trash icon 🗑 to delete a folder and all its timbres.
Working with individual timbres
- Use the search box to filter timbres by name across the entire library.
- Click → on any timbre to open it in the Timbre Editor.
- Click ✎ to rename a timbre.
- Click 🗑 to delete a timbre from the library.
Saving the Library
- Click ⬇ Guardar .json to save the entire library (with folder structure) as a JSON file. This is your backup — save it often.
The library is also saved automatically in your browser's local storage. But always keep a .json backup — browser storage can be cleared.
✏️ Timbre Editor
The Timbre Editor lets you edit any of the 64 user timbre slots. The MT-32 uses LA (Linear Arithmetic) synthesis, which combines PCM samples with digital subtractive synthesis.
Selecting a timbre
The left panel shows all 64 timbre slots (1–64). Click any slot to load it into the editor. The currently selected slot is highlighted in amber.
Structure selector
Each timbre has up to 4 Partials combined according to a Structure. Click one of the 8 structure buttons to change how Partials are routed. The diagram shows the signal flow — ring modulation and mixing combinations.
Partial editor (tabs 1–4)
Click any of the Partial 1 – Partial 4 tabs to edit that partial. Each partial has:
| Section | Parameters |
|---|---|
| WG (Wave Generator) | PCM Wave selection, Pitch Coarse/Fine, Keyfollow, Bender, LFO mod, Pulse Width and PWM |
| TVF (Time Variant Filter) | Cutoff, Resonance, Keyfollow, Bias Point & Depth, Envelope (Time 1–4, Level 1–3) |
| TVA (Time Variant Amplifier) | Level, Velocity sensitivity, Bias Point 1 & 2 & Depth, Envelope (Time 1–4, Level 1–3) |
| LFO | Rate, Delay, Pitch/Filter/Amplitude depth |
TVF & TVA Bias editors
The bias editors show an interactive keyboard. Drag the marker along the keyboard to set the bias point. For TVA, right-click on the keyboard to toggle the direction of each bias point (above or below the key).
Sending a timbre to the MT-32
After editing, click ⬆ Enviar al MT-32 in the right panel to write the current 64-slot set to the hardware.
The MT-32 stores edits in RAM. They will be lost when powered off unless you save them to a .syx file first, or write them with Send All.
🎹 Performance
The Performance section configures how the MT-32 responds to incoming MIDI across its 8 parts (plus the rhythm part).
For each part you can set:
- MIDI channel — which channel this part listens on (1–16)
- Timbre assignment — which timbre number (1–64 for user, or preset bank) is assigned to this part
- Volume and Pan — part level and stereo position
- Key range — the note range this part responds to
- Reverb switch — whether reverb is applied to this part
Click ⬆ Enviar al MT-32 in the right panel to send the current Performance setup to the hardware.
⚙ System
The System section controls the MT-32's global reverb settings. These are the only system parameters exposed in EMETERIO — other MT-32 system parameters (master volume, partial reserve, etc.) are intentionally not included to keep the editor focused and avoid accidental changes to the hardware's global state.
| Parameter | Description |
|---|---|
| Reverb Mode | Room, Hall, Plate, or Tap Delay |
| Reverb Time | Decay length of the reverb tail |
| Reverb Level | Wet/dry amount of reverb in the mix |
Click Enviar System to send the reverb settings to the MT-32 without touching the timbres or other data.
🥁 Rhythm
The Rhythm section in EMETERIO is designed around the Roland TR-8 drum machine as the trigger source. It uses 11 fixed slots — the last 11 of the 64 user timbre area (M54–M64) — each permanently mapped to a TR-8 pad MIDI note.
Each rhythm slot is a fully editable user timbre (LA synthesis), not a raw PCM drum sample. You can open any rhythm slot in the Timbre Editor and edit it like any other timbre — with one deliberate limitation: rhythm timbres are restricted to a maximum of 2 active Partials. This prevents the clicks, pops, and noise that occur when the MT-32 runs out of Partial RAM while the drum part is firing rapid notes. Keeping it at 2 Partials per slot ensures clean, reliable playback.
Fixed MIDI note mapping (TR-8)
Each of the 11 rhythm slots is hardwired to the MIDI note that the corresponding TR-8 pad sends. You don't configure these — they're fixed in the SysEx Rhythm Setup that EMETERIO writes to the MT-32:
| Slot | TR-8 Pad | MIDI Note | Note Name |
|---|---|---|---|
| M54 | BD — Bass Drum | 36 | C2 |
| M55 | SD — Snare Drum | 38 | D2 |
| M56 | LT — Low Tom | 43 | G2 |
| M57 | MT — Mid Tom | 47 | B2 |
| M58 | HT — Hi Tom | 50 | D3 |
| M59 | RS — Rim Shot | 37 | C#2 |
| M60 | HC — Hand Clap | 39 | D#2 |
| M61 | CH — Closed Hi-Hat | 42 | F#2 |
| M62 | OH — Open Hi-Hat | 46 | A#2 |
| M63 | CC — Crash Cymbal | 49 | C#3 |
| M64 | RC — Ride Cymbal | 51 | D#3 |
Editing rhythm timbres
To edit a rhythm sound, click on its slot in the Library or Timbre Editor (slots 54–64). The Partial editor will open normally — just remember the 2-Partial limit. You can design any LA synthesis sound: oscillator waves, filter, envelope, LFO. The result is a fully synthesized drum hit, not a sample playback.
Per-slot controls (Rhythm section)
In the 🥁 Rhythm tab, each of the 11 slots has three adjustable parameters:
| Parameter | Range | Description |
|---|---|---|
| Level | 0–100 | Output volume for this drum hit |
| Pan | -7 to +7 | Stereo position (0 = center) |
| Rev | On / Off | Whether reverb is applied to this slot |
Changes are sent to the MT-32 immediately when you release a slider or toggle reverb. To write the full Rhythm Setup to permanent memory, click ⬆ Enviar al MT-32.
The MIDI note mapping follows the General MIDI drum standard for most pads, so the rhythm section works with any drum machine or DAW that sends notes on those pitches — not just the TR-8. Just make sure your device sends on the same MIDI channel as the MT-32's rhythm part.
Send & Receive
The right-hand panel handles all MIDI transfer operations.
Sending to the MT-32
- ⬆ Enviar .syx al MT-32 — sends everything: timbres, system, performance and rhythm in one operation. Use this for a full restore.
- Enviar System — sends only the system settings block.
- ■ Detener — aborts a transfer in progress.
A progress bar shows the current transfer. Large SysEx transfers take a few seconds — do not power off the MT-32 during transfer.
Loading from a .syx file
- Click 📂 Cargar .syx to load a SysEx file into the editor slots. This does not send to the hardware automatically.
- After loading, click Send All to write to the MT-32.
Always save a .syx backup before sending new timbres — the MT-32's RAM will be overwritten and the previous state cannot be recovered.
SYX Files
SysEx (.syx) files are the universal format for storing MT-32 data. EMETERIO can both load and save them.
- ⬇ Guardar como .syx — exports the current 64 timbres as a .syx file you can keep as a backup or share.
- Standard MT-32 .syx files from other sources (editors, archives) can be imported directly into the Library or the edit slots.
SysEx files from the original Roland MT-32 sysex format (header F0 41 1n 16 12) are fully compatible.
Troubleshooting
No MIDI devices appear in the dropdown
- Make sure you clicked Allow when Chrome asked for MIDI permissions.
- Try clicking ⟳ to refresh the device list.
- Plug in your interface before opening the editor.
- Try a different USB port or cable.
Send All completes but the MT-32 doesn't change
- Check that MIDI OUT from your interface is connected to MIDI IN on the MT-32.
- Verify that the correct output port is selected in the editor.
- Make sure your MT-32 has SysEx reception enabled (check the MT-32 system menu).
Transfer gets stuck or times out
- Click ■ Detener to abort and try again.
- Close any DAW or other MIDI software that may be blocking the port.
- Some cheap USB-MIDI interfaces drop SysEx bytes at high speed — try a quality interface.
Editor works but sounds are wrong after transfer
- The MT-32 may need a moment after receiving SysEx. Try triggering a note after a short pause.
- Check that the Partial Reserve settings in System add up correctly (should not exceed 32 total).
Post in the Reddit thread where you found this tool — include your browser version, OS, and MIDI interface model.