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CVA-7 - CV Analyzer for Reason

This project contains the full source code for the free rack extension CVA-7 for Reason, the music DAW produced by Reason Studios. Check the CVA-7 website for more details.


  • The source code is released following Reason Studios decision to open up the Rack Extension SDK platform allowing for this kind of project to be made publicly available

  • It is mostly meant as an example of a fully functional RE and the code is sparsely documented. I have since used C++ more intensively (in Jamba and other VST plugins) and would probably make very different implementation decisions now, especially being more familiar with "modern" C++.

  • The master branch is currently unreleased as the code has been updated to use re-cmake and RE SDK 4.2.0 but there are no new features. The advantage is that it is much easier to build and can be build on both macOS and Windows10.


  • This project requires CMake (minimum version 3.13) properly installed (cmake executable must be in your PATH)
  • This project currently expects RE SDK 4.2.0 or 4.1.0 to be installed on the machine (it will not download it for you)
  • Due to the RE SDK requirements, this project also requires python 3 to be installed
  • It has been tested on macOS 10.14.6 with Xcode 9 installed
  • It has been tested on Windows 10 with Visual Studio 16 2019 build tools


  • Design contains the Pixelmator files used to create the graphics
  • GUI2D is a standard RE SDK folder which contains the images (png format) as well as device_2D.lua and hdgui_2D.lua files which defines the UI
  • Resources is a standard RE SDK folder which contains the strings (English only) displayed in the UI
  • src/cpp contains the C++ source code for the device
  • info.lua, motherboard_def.lua and realtime_controller.lua are standard RE SDK files for defining the device
  • display.lua is the standard SDK file which contains the lua code for the UI (various custom displays)
  • is the python script you use to configure the CMake build

Implementation notes

  • Because this device was originally created for SDK 2.2, it only uses C++11 (but be aware that it is a limited (by the SDK) version of C++11). The re-common framework it depends on uses C++17.

  • In order to render the waveform of the CV signal in the UI, the implementation uses 256 properties to pass the necessary information from RT to UI. It uses a PendingUpdates class to limit the amount of changes per batch. RT owned strings were introduced in SDK 2.5 in order to handle this kind of use case (which would translate into 1 RT owned string property instead of 256 individual properties) and is most likely a much better design.

  • The class Motherboard models the motherboard_def.lua from a C++ point of view

  • The properties use a property manager (IJBoxPropertyManager) which automatically processes the iPropertyDiffs provided on each batch to update the properties.

  • The Device class represents the entry point and is the class that is the privateState in the C-style JBox_Export_RenderRealtime api. It contains 2 copies of the DeviceState class: one being the state from the previous batch and one the state for the current batch. At the end of the batch, the current state is copied into the previous state. This allow to see if values have changed and respond appropriately. This design inspired the first iteration of the Jamba framework (VST) but with refinement it then led to having the Property (aka Parameters in VST world) themselves hold the previous and current values which I now believe is a better design. I may retrofit this design in a future implementation...

Note about the RE SDK location

You can install the SDK wherever you want on your system and provide it as an argument to the script. Or you can install (or create a link) in a default location:

  • /Users/Shared/ReasonStudios/JukeboxSDK_<RE_SDK_VERSION>/SDK for macOS
  • C:/Users/Public/Documents/ReasonStudios/JukeboxSDK_<RE_SDK_VERSION>/SDK for Windows

Also note that the RE2DRender program needs to be unzipped and is expected to be a sibling of SDK (can be changed as well).

Quick Starting guide

Step 1 - Configure the build

Invoking the creates a build directory in the directory where the command is run. Although it is strongly recommended to run this command outside the source tree, the build directory is excluded in .gitignore and since everything is contained within the build folder it is easy to clean after the fact.

Running the python3 -h command will print the usage.


Depending on how python is installed on your system you may have to invoke it differently.


This script is expecting the cmake command line tool to be in the path (use cmake -version to confirm it is properly installed).

If you have setup the RE SDK in its default location, as specified above, simply run python3 otherwise use the -p option to specify its location.

Step 2 - Install the plugin

After running the configure script, simply go into the newly generated build folder and run install (resp. re.bat install). This will build the plugin and install it in its default location.


Simply run -h (resp. re.bat -h) for help with the command


This script is expecting the cmake command line tool to be in the path (use cmake -version to confirm it is properly installed).

Step 3 - Try the plugin

You can then open Recon and load the newly built CVA-7 rack extension (you will find it under Utilities | pongasoft | CVA-7 CV Analyzer)


The plugin will only appear in Recon not Reason

Changing the code, Debugging, etc...

If you want to change the code, run a debugger, etc... you can check the instructions for the re-blank-plugin which explain how to generate an XCode project, load it in an IDE, etc...

Release notes

master (unreleased)

  • Upgraded to use re-cmake (removed all unnecessary files and added CMake build files)
  • Upgraded to use RE SDK 4.2.0
  • Builds properly on Apple chipset
  • Fixed old code taken from a wip branch (display was broken)
  • Use re-common 3.0.0 (simplify property creation with mini string library / printf)

1.0.1 - 2021/06/23

  • Fixed image sizes to work in Recon and future versions of Reason (fix for filmstrip images not being multiple of 5)

1.0.0 - 2016/11/30

  • First release.



CVA-7 is a free rack extension for Reason, the music DAW produced by Reason Studios. It is a utility which lets you analyze a CV signal in various ways







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