NRPN to CC — VST3

A VST3 plugin (VST3 only) of type instrument (VSTi) that receives MIDI, passes through everything that is not NRPN, and converts NRPN messages into CC, sending the result to its MIDI output.

Why an instrument and not a "MIDI effect"? Cubase does not load VST3 MIDI-effect plugins in its MIDI Insert slots (those accept only Cubase's native MIDI plug-ins), and as an audio insert it would not receive the track's MIDI. An instrument, instead, is fed the whole MIDI stream of the track: so the plugin receives the NRPN messages and can emit the CC on its output, which you route to a virtual instrument or an external MIDI track. As a bonus, the controller's MIDI port is opened by Cubase, not by the plugin: no port conflict.

What it does

• Receives NRPN (CC 99/98 = parameter number, CC 6/38 = value).
• Generates a CC with automatic mapping: CC number = NRPN parameter number (low 7 bits).
• From the interface you can set:
  • Input channel (Omni or 1–16): which channel to listen to.
  • Output channel (Same as input or 1–16).
  • Output format:
    • 7-bit auto-range (default) → a single CC. The plugin learns, per NRPN (and per channel), the maximum value it receives and scales it to 0–127. Generic, with no device-specific tables: switches (max 1) become 0/127, knobs become a smooth 0–127. Do one full sweep of each knob to calibrate it; the learned ranges are saved in the project. The Reset learning button clears them.
    • 7-bit fixed scale → a single CC scaled with a fixed maximum (Max (fixed scale)), useful when you know the range and want deterministic behavior.
    • 14-bit (MSB+LSB) → two CCs: CC#n = MSB and CC#n+32 = LSB (high resolution).
  • Max (fixed scale): used only by the "fixed scale" mode.
  • Pass through original NRPN: if enabled, the raw NRPN messages are forwarded too, in addition to the CC.
  • Filter repeated CC (default ON): in 7-bit mode, avoids sending consecutive CCs with the same value (useful because scaling 0–255 → 0–127 makes many steps map to the same CC).
  • Monitor: shows the last NRPN received, the CC sent, and a bar of the outgoing CC value.

Note on MIDI ports: a VST3 plugin inserted in a track does not open hardware ports. The physical port (your MIDI interface) is chosen in the DAW's track routing. In the plugin you choose the channel; the port is handled by Cubase.

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Usage scenario

The screenshot below shows the typical setup in Cubase Pro:

1. Create an instrument track and load NRPN to CC on it (NRPN to CC 01 in the screenshot). Set this track's MIDI input to the instrument/controller whose NRPN messages you want to translate (e.g. your hardware synth, or "All MIDI Inputs"), and enable input monitoring so the MIDI reaches the plugin.
2. Create a second track hosting the target instrument — another virtual instrument (VSTi) or an external device (OB-Xtrm3 01 in the screenshot).
3. Set the target track's MIDI input to NRPN to CC's MIDI output. The signal flow becomes: source → NRPN to CC → target instrument.
4. Non-NRPN messages pass through untouched; NRPN messages are converted to CC (in the screenshot NRPN #45 → CC #45), so the target instrument receives standard CC it can map or MIDI-learn. The Monitor shows the live conversion.

This example uses Cubase, but the same approach works in any DAW: host NRPN to CC as an instrument, feed it the source MIDI, and route its MIDI output to the target instrument/track.

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Prerequisites (Windows)

You need a C++ compiler and CMake:

1. Visual Studio 2022 or later, Community edition (free) — during installation select the "Desktop development with C++" workload. It includes the MSVC compiler, the Windows SDK and the "C++ CMake tools" (hence CMake). Download: https://visualstudio.microsoft.com/downloads/
2. Git.

(Alternatively you can install CMake standalone from https://cmake.org/download/ plus the Build Tools for Visual Studio, but the full IDE is the simplest route.)

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Building

Open the "Developer PowerShell for VS" (from the Start menu) and go to the project folder:

cd "path\to\NrpnToCc"

Configure (the first time this downloads JUCE automatically: a few minutes):

cmake -B build -G "Visual Studio 17 2022" -A x64

On Visual Studio 2026 use the generator "Visual Studio 18 2026" instead.

Build in Release:

cmake --build build --config Release

The compiled plugin is at:

build\NrpnToCc_artefacts\Release\VST3\NRPN to CC.vst3

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Installation

The build does not copy the plugin automatically. Copy the NRPN to CC.vst3 folder into one of these locations:

• C:\Program Files\Common Files\VST3 (all users — requires admin)
• %LOCALAPPDATA%\Programs\Common\VST3 (current user only — no admin)

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Using it in Cubase (recommended routing: instrument rack)

Goal: controller → plugin → (pass-through + CC) → virtual instrument / external instrument.

1. Rescan the VST3 plugins (Studio → VST Plug-in Manager → Update). The plugin appears among the instruments (Instrument), not among the inserts.
2. Open the instrument rack: Studio → VST Instruments (F11). Add NRPN to CC. When Cubase asks to create an associated MIDI track, accept.
3. "IN" track (the one created in step 2, pointing at the plugin):
   • MIDI input = your controller (or "All MIDI Inputs").
   • Enable Monitor (the speaker icon) or record-enable, so MIDI reaches the plugin.
   • Open the plugin GUI: when the controller sends NRPN, the Monitor must light up.
4. Enable the plugin's MIDI output: in the instrument rack, on the NRPN to CC slot, enable the plug-in MIDI output (in many versions there is a small "MIDI Out"/connector control on the slot; its position varies with the Cubase version).
5. "OUT" track (new MIDI track):
   • MIDI input = NRPN to CC (the plugin's MIDI output now appears in the input list).
   • MIDI output = the desired destination: a virtual instrument (another instrument track) or an external MIDI port (hardware synth).
   • Enable Monitor on this track so the converted stream reaches the destination.

Final flow: controller → IN track → NRPN to CC → OUT track → instrument/hardware.

Cubase 15 Pro — specific notes:

• Use the rack (F11), not a plain instrument track: only the rack instance reliably exposes the plugin's MIDI output as a selectable input on another track.
• In Cubase 15 the instrument's MIDI output appears automatically among the MIDI inputs: no global switch is needed.
• If "NRPN to CC" does not appear among the inputs in step 5: close/reopen the routing window or reload the project after adding the instrument in the rack.

MIDI behavior

• Notes, pitch bend, regular CC, etc. → pass through unchanged.
• NRPN (CC 99/98/6/38) → converted to CC (automatic mapping: NRPN number → CC number).
• Raw NRPN messages are absorbed (not forwarded), unless you enable Pass through original NRPN in the GUI.

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Project structure

NrpnToCc/
├─ CMakeLists.txt          # VST3-only build, downloads JUCE via FetchContent
├─ LICENSE                 # GNU GPL v3
└─ Source/
   ├─ PluginProcessor.h/.cpp   # NRPN -> CC logic
   └─ PluginEditor.h/.cpp      # interface (channels, modes, monitor)

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License

This project is distributed under the GNU General Public License v3.0 (see LICENSE).

The plugin is built with JUCE, used under its GPLv3 license. As a result this project is released as GPLv3 free software. JUCE is not included in the repository: it is downloaded automatically by CMake (FetchContent) at build time.

© GPR Music Project.