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Blue Cat Audio - Software Made by Musicians for Musicians
Blue Cat's Plug'n Script
Blue Cat's Plug'n Script
"Craft your own effects and instruments"
Price: 99€ or $99 (tax incl.)
Blue Cat's Plug'n Script - Scriptable audio / MIDI effects processor and virtual instrument

Blue Cat's Plug'n Script is an audio and MIDI scripting plug-in and application that can be programmed to build custom effects or virtual instruments, without quitting your favorite DAW software.

MacOSUniversal BinaryWindows Vista or newerWindows x64 (64-bit)VSTVST3AAX64-bit AAXAudio Unit
Also in Bundles: All Plugins Pack / Crafters Pack

With this plug-in, you can write your own plug-in with very little knowledge about programming. If you do not care about programming, Blue Cat's Plug'n Script can also be used as a regular multi effects processor with existing scripts or to get someone else write this very particular utility you have been searching for years and cannot find anywhere.

If you are an experienced programmer, you will find in Plug'n Script a powerful development environment for audio plug-ins: prototype algorithms quickly, generate a state of the art graphical user interface (GUI) without a single line of code, and export a VST, VST3, AAX, or Audio Unit plug-in, right from within your favorite DAW! Creating a plug-in has never been so fast!

This plug-in has been in our lab for several years and has been used to prototype lots of our existing plug-ins. It supports both scripts distributed as source code and pre-compiled binary scripts.

For source scripts, it uses the high performance AngelScript scripting engine, originally developed for video games, with a JIT compiler that helps compiling scripts into machine code for optimal performance. Starting with version 2, the plug-in also supports native (compiled) code and can load binary scripts built from C or C++ (or any language that can export C functions, such as Delphi, Fortran, .Net...), using the same interface as the angelscript version.

The syntax of the AngelScript language is close to Java, C#, C++ or JavaScript, making it very easy to learn. It is also convenient to reuse your scripts into native code, or integrate code snippets found on the web into your script. Also, switching between angelscript and binary versions of the same script is very easy, requiring very few changes.

The plug-in includes dozens of audio and MIDI processing scripts as well as several virtual instruments and utilities to enhance your workflow. They can be used as is, or as examples to get started to write your own scripts. User scripts can be shared in the scripts repository, which also includes the factory scripts and native projects for reference.

To build complex effects chains using multiple scripts, you might be interested in Blue Cat's PatchWork, which can host multiple instances of this plug-in in series or parallel. While writing scripts, you might also want to use our analysis tools to check their effect on the signal.

Main Features:

  • Audio and MIDI scripting plug-in.
  • Build your own Audio and MIDI effects or virtual instruments.
  • Export your effect or instrument as an independent VST, VST3, Audio Unit or AAX plug-in.
  • Simple scripting syntax, using either the AngelScript language (similar to C++, Java or javascript) or C/C++ for native code.
  • Native binary scripts support (compiled C, C++ or Delphi, Fortran...).
  • Fully customizable user interface that adapts to scripts automatically. Build your own using Blue Cat's KUIML language.
  • Up to 48 input parameters and 32 outputs, with full MIDI and automation control.
  • Use your favorite Integrated Development Environment (IDE) for editing.
  • Integrated JIT (Just In Time) compiler for optimal performance (scripts are not interpreted but compiled).
  • Includes 57 scripts with source code and 267 presets for sound synthesis, MIDI FX, audio FX (comp, gate, tremolo echo, filters, looper...), waveform generation, file playback/recording and more.
  • Side chain input and auxiliary outputs support.
  • Surround support (up to 8 audio channels).
  • Download free scripts from our audio & MIDI scripts repository.

Blue Cat Audio Standards:

  • Available as a standalone application and in most plug-in formats for Mac and Windows.
  • Full MIDI control and automation support, MIDI Learn.
  • No CPU load on idle: processing shuts down when fed with silence (optimal CPU usage).
  • Customizable user interface with transparency & zoom.
  • Automation and MIDI output: record output parameters as automation curves or send MIDI CC messages to other plug-ins for powerful side chain effects.
  • Smooth Bypass: noiseless plug-in activation / deactivation.
  • Undo/Redo.
  • Full featured integrated presets manager.
  • Copy/paste the state of the plug-in between instances.
  • Any sample rate supported.

Typical applications: Audio and MIDI scripting, virtual instruments programming, VST plug-in development, digital signal processing (DSP), Multi-effect processor, algorithm prototyping, audio dsp learning.

Blue Cat's Plug'n Script - Choose your style and let the plug-in generate the graphical user interface (GUI) for you. Blue Cat's Plug'n Script - Scriptable audio / MIDI effects processor and virtual instrument Blue Cat's Plug'n Script - Output parameters for audio analysis and parameter modulation Blue Cat's Plug'n Script - Real time MIDI events processing Blue Cat's Plug'n Script - Write your own Virtual Instruments: included drawbar organ example (additive synthesis). Blue Cat's Plug'n Script - Use your favorite Integrated Development Environment (IDE) for scripts editing Blue Cat's Plug'n Script - Script example for a tremolo audio effect Blue Cat's Plug'n Script - Write custom layouts for your graphical user interfaces (GUI) using the included widgets.

User Comments & Reviews

"Plug'n Script is a very original and powerful piece of software. A simple and intuitive interface, which actually opens a full world of experimentation. Very convenient to prototype new signal processing ideas in seconds. The example scripts are a mine of information, both for audio programmers and beginners. A unique and extremely powerful plugin!" - Charles Verron, Founder -

"An amazing piece of software, it makes possible prototyping new digital signal processing algorithms in a few minutes. And now with the latest version of Plug'n Script, the scripts are running really fast!

Great tool for newcomers who want to familiarize with audio development or for professionnal developers who want to hear quickly what their algorithm sounds like." - Ivan Cohen, Developer - Musical Entropy.

To add your own comment about this product, please contact us.

Demo Limitations:

  • 5 instances of the plug-in allowed per session.
  • The effect is bypassed for half a second every minute.
  • Exported VST plug-ins display a demo message and will stop processing after 10 minutes.

System Requirements


  • An Intel or Apple Silicon processor.
  • Mac OS 10.9 or newer.
  • For the plug-in, any VST / Audio Unit / AAX compatible application (64-bit) .
  • For the standalone application, a Core Audio compatible audio interface.


  • An SSE2-enabled processor (Pentium 4 or newer).
  • Microsoft Windows Vista, Windows 7, 8 or 10.
  • For the plug-in, any VST / AAX compatible host software (32 or 64 bit).
  • For the standalone application, an ASIO, MME or WASAPI compatible audio interface (ASIO recommended).

For more information about supported platforms, see our Knowledge Base.

Versions History

V3.34 (2024/05/14)

  • Extended user interface programming capabilities with KUIML 2.7.4 support (User Interface programming language).
  • Scripting engine update, with improved performance.
  • Unlimited parameters: for plug-ins developers, you can now configure the number of i/o params and strings via a configuration file.
  • Offline processing status (non-realtime rendering) is now available from the processBlock function.
  • AAX plug-in now reports the recording status (in recent versions of Pro Tools that support it).
  • Fixed missing floatToString,intToString and uIntToString functions for dsp scripts on Apple M1.
  • AAX Atmos format is now available for exported plug-ins too.
  • Graphical user interface refresh performance improvements.
  • Improved resampling when the application starts streaming audio as a network server with Connector.
  • Fixed a couple of issues with undo/redo.
  • Ableton Live 11: Fixed VST3 MIDI input not detected.
  • Fixed drag and drop that did not work within a 2 pixels margin at the border of drag source widgets.
  • Fixed file drag and drop issues on Mac when using system::filepath applicative type.
  • Mac: Fixed negative values not properly sent to DSP when entering them in text box after double clicking on a knob.

V3.33 (2022/12/12)

  • actual parameter names (as set in the scripts) should now be visible in automation lanes in most host applications (may require a session reload in some cases).
  • VST: improved parameter value display in some host applications.
  • The application is now using Apple's hardened runtime, and the installer has been notarized to avoid security warnings on Mac. You may have to add the --force option to code signing command line if you are signing your binaries.
  • Added Apple Silicon support for AAX plug-in format.
  • Added Ambisonic and alternate surround formats support for Pro Tools (Plug'n Script only: not yet for exported plug-ins).

V3.32 (2022/06/23)

  • Single Installer on Mac (all plug-ins formats).
  • Full Apple Silicon (M1 processor) support.
  • New "network slave" mode to run as an audio/MIDI processing server for the Connector plug-in.
  • Windows: ASIO Control panel can now be launched from the audio settings window in the application.
  • Audio engine can now be restarted from the audio settings window in the application.
  • Dropped 32-bit support on Mac.
  • Now requires MacOS 10.9 and newer.
  • Improved MIDI events timing precision in the application.
  • Added MIDI tap tempo support for standalone application.
  • Standalone application can now send MIDI events to external devices.
  • Select individual MIDI I/O in standalone application.
  • In most plug-in formats, internal audio I/O configuration can now be selected regardless of the configuration defined by the host.
  • Improved MIDI & automation control settings with lock, reset and "save as global setting" capabilities.
  • The plug-in and app can now send MIDI events back to a control surface when MIDI-enabled parameters are modified in the user interface.
  • It is now possible to export plug-ins with an unlimited number of parameters.
  • The user interface does not throw errors anymore when using more than 48 input parameters in a script (they are simply not displayed).
  • Fixed latency compensation changes not always picked up by host applications.
  • VST3: fixed random crash in Ableton Live 11 upon load.
  • VST3: fixed parameters update issues in Studio One when bouncing tracks.
  • Windows: fixed an issue with unicode window titles.
  • MacOS: fixed export window colors in dark mode.
  • MacOS: fixed plug-in editor positioning issues in some hosts with some particular zoom values

V3.31 (2021/02/16)

  • Arrow keys can now be used to navigate presets, in the main view or in the presets browser.
  • Next/Previous preset can now be triggered by MIDI CC commands.
  • New DSP workload meter in the status bar.
  • Smoother presets switching.
  • Improved smooth plug-in bypass.
  • Level meters do not use CPU anymore when the user interface is closed.
  • Many optimizations for faster GUI loading and reduced memory usage.
  • Improved performance for native DSP scripts.
  • Improved plug-in loading performance, especially when having many user presets.
  • Full Unicode support added to Windows platform.
  • New Experimental Xml parser/writer for Angelscript.
  • new KUIML actions to display presets or global settings windows: OpenPresetsSettings, OpenGlobalSettings.
  • KUIML errors can now be redirected to a log file (log_file_path directive in SKIN)
  • KUIML errors display in popup window can be disabled (show_messages="false" in SKIN)
  • window.loaded attribute is now properly set to false and sends events when the plug-in window is closed.
  • updated Angelscript filesystem object (fixes several issues with file dates).
  • VST3: fixed a GUI update issue when using automation and long buffers in Cubase (parameters values jumping).
  • Fixed an issue with random Audio Unit validation failures with exported plug-ins on MacOS older than 10.12.
  • Fixed transport info sometimes not properly initialized for exported plug-ins using native DSP.
  • Fixed an issue with endValues not properly set when using processBlock in exported plug-ins (Native scripts only).
  • Fixed crash when defining actions after using the content attribute in INCLUDE directive.
  • Mac: fixed intToString Angelscript function crash.
  • Mac: fixed GUI performance issues on native P3 displays and improved performance on other displays.
  • Mac: fixed mouse wheel that required large movements to change parameter values.
  • Mac: fixed mouse cursor flickering issues.
  • Mac: fixed Esc key not closing fine edit parameter dialog.

V3.3 (2020/06/15)

  • Custom graphics and resource files are now be copied when exporting scripts as independent VST, VST3, AU or AAX plug-ins (SCRIPT_DATA_PATH folder).
  • New version of the KUIML GUI programming language (2.7), with new widgets, new mouse and keyboard events handling features, system script function to execute shell commands and more.
  • New version of the Angelscript Engine (2.34).
  • New high resolution graphics for knobs.
  • New background mode ("None") to create entirely custom user interfaces.
  • New icon for the Plug'n Script Application.
  • Reduced disk footprint.
  • Fixed crash in exported VST3 plug-in when using input strings in scripts.
  • Fixed crashes when using build-time script in KUIML widgets.
  • Fixed gui.capture objects that could be exposed twice in KUIML objects.
  • Fixed png or svg images alpha mask not properly loaded (was ignored)
  • Fixed ignore_missing attribute for LOAD_FONT that still triggered an error.
  • Mac application now fully supports dark mode on Mac OS Mojave and newer.
  • Mac: fixed settings panel rendering issues in dark mode on Mac OS Mojave and newer.
  • Mac: Fixed keyboard not responding in registration panel in some host applications (LUNA, Garage Band...).
  • Mac: Fixed demo version that could hang Logic when reloading projects using the plug-in.
  • Mac: fixed Retina scaling issue on buffered widgets in apps built with Mac OS 10.14 SDK and newer.

V3.2 (2019/08/30)

  • DSP script can now be encrypted upon export.
  • DSP script can now define output strings to share any kind of data with the user interface.
  • Export plug-in in AAX format for Pro Tools and Media Composer (for registered AVID developers).
  • New presets browser with built-in search (also available in exported plug-ins).
  • New version of the KUIML GUI programming language: drag and drop, canvas widget, build time scripting, lazy loading and more.
  • New oscilloscope sample script (output strings feature demo).
  • MIDI Program Change preference is now saved into session instead of global preferences, so each instance can now use different MIDI channels. It is also saved in the user default preset.
  • VST3: added program change support for VST3 plug-in format.
  • VST3: added MIDI output support for VST3 plug-in format.
  • Faster GUI rendering on recent Mac OS systems (up to 5x faster on level meters).
  • Improved GUI loading time when using many widgets.
  • Fixed an issue with MIDI control that did not always work properly when the plug-in GUI was open.
  • VST: the user interface is now properly resized in Cubase on Windows.
  • Improved plug-in and app listing in Windows 10 start menu.
  • Fixed wrong value set by SetProgram function in built-in MIDI library.
  • Fixed built-in library not always copied to user documents folder.
  • Fixed scripts menu order on Mac OS Sierra and newer.
  • Fixed: native widgets in custom user interfaces used to be visible before the layout was done.

V3.1 (2018/11/30)

  • Now available as a standalone application.
  • Export plug-in in VST3 and Audio Unit plug-in formats.
  • Faster graphical user interface loading.
  • New version of the Angelscript engine (2.32) with improved performance and new add-ons (datetime, filesystem).
  • Last loaded preset is now remembered in session and displayed in the presets menu.
  • Plug-in state can now be reverted to the last loaded preset.
  • Improved scalable graphics for icons and buttons.
  • Dropped support for legacy RTAS and DirectX plug-ins formats.

V3.01 (2017/10/19)

  • Fixed: VSTs exported for Mac were not properly detected by host applications.

V3.0 (2017/10/17)

  • Brand new GUI design, with improved usability and touchscreen support, fully zoomable.
  • Scripts can now be exported as independent VST plug-ins.
  • Customize the user interface in the plug-in (no code required), or write your own layout for each script.
  • Separate player and editor modes for optimal workflow.
  • Parameters display format can now be set by scripts.
  • Retina displays support on Mac (high resolution for text and vector graphics).
  • Changed demo limitations: up to 5 instances allowed, bypass time changed to half a second, and bypass parameter is not affected anymore.
  • New installer on Mac.
  • New version of the Angelscript engine (2.31.1).
  • Fully compatible with previous versions of the plug-in.
  • Warning: changed the identifier of the VST3 version on Mac. See this post for more details.
  • Fixed minor issues on Mac OS High Sierra.
  • Fixed native file recorder script issues (file names were not properly generated for rotation).
  • Fixed MIDI channel issue with VST3: MIDI channel for note events was offset by one in the VST3 plug-in version.
  • Removed specific mono and stereo versions for the VST plug-in - please unintall previous versions first if you do not need them (new installer will not remove them).
  • Dropped support for Windows XP and Mac OS X 10.6 and earlier.

V2.1a (2016/03/04)

  • (VST only) Fixed a crash when loading the VST version in Ableton Live.

V2.1 (2016/03/03)

  • VST3 plug-in format support, with improved external sidechain compatibility for Cubase and Nuendo.

V2.0 (2015/11/25)

  • External side chain and auxiliary outputs support (up to 16 audio outputs).
  • Native C/C++ scripts support for optimal performance and flexibility.
  • KUIML 2.0 user interface language support to build custom user interfaces, with additional scripting capabilities.
  • New DSP scripts, delivered with full angelscript and C++ source code.
  • 21 new custom skins included.
  • User documentation (html or pdf) can now be added to scripts.
  • Custom skins can be selected directly from the main menu.
  • Presets can now be selected using MIDI Program change and bank select messages (can be activated with the presets menu/MIDI Program Change item).
  • Last loaded preset can now be saved directly from the presets menu without having to select the file.
  • VST: fixed latency compensation reporting in Cubase (no need to re-enable the plug-in to update the latency anymore).

V1.1 (2014/10/01)

  • Audio Unit can now be loaded as a MIDI effect in Logic Pro X.
  • The user interface now displays switch buttons for boolean parameters instead of knobs.
  • Discrete parameter values can now be selected from a dropdown menu.
  • New API: scripts can now use plain strings as user input.
  • New API: scripts can now read and write files.
  • New scripts and presets: added audio player and recorder scripts and a wave file utility class.
  • Developers can now share their scripts on a dedicated GitHub repository.
  • Fixed: implemented pass-thru for MIDI events when no processing function is declared (default script for example).
  • Fixed: Audio Unit Synth version did not appear as an Instrument.
  • Fixed: script was reloaded when starting playback in Reaper, and the effect was not applied immediately.
  • Fixed: RTAS version could freeze Pro Tools 9 and earlier at startup.

V1.0 (2014/09/18)

First release.