Reason Studios developer tools "Rack Extensions take all the good things about plugins and then marries it to all the good things about Reason."
Ernst Nathorst-Böös, CEO

Design it, code it, test it, ship it.

With Reason Studios' Rack Extension platform, developers can move faster from initial idea to finished product than ever before. Regardless of whether your skills lie in hardcore DSP coding or in creating beautiful samples, the Rack Extension platform has all the tools you'll need to develop stunning instruments and effects and bring them to market with minimum effort and maximum support.

The recently updated developer toolkit adds features and tools for developers to create even more advanced and great-looking instruments and effects. With the Instrument Development Toolkit, it's easier than ever to build advanced instrument Rack Extensions, even without prior coding experience.

Rack Extensions are full citizens of the Reason Rack, cross-platform compatible, copy-protected, future-proof, and easy to sell direct to Reason users in the Reason Studios Shop. How to become a developer.

"We've already transformed a few of our current products to Rack Extensions. The back panel on each device with the many CV options truly reveals the power of Reason and Rack Extensions. Our next release is a dedicated Rack Extension synthesizer."

Rob Papen, synth pioneer

Rack Extensions at a glance Rack Extensions are plugin additions for the Reason Rack. Using a comprehensive development kit provided by Reason Studios, third party developers can create instrument and effect units to be used inside of Reason.

Write once. Release everywhere.

Rack Extensions are cross platform, and will continue to work in the next version of Reason, and the next after that. You focus on building cool products, not maintain code. The Rack Extension platform will be kept up to date with current operating systems, removing the need for developers to update their products.

Full Citizens of the Reason Rack

A Rack Extension lives inside the Reason Rack, like any other rack device. They are fully integrated in the Reason user experience and work seamlessly with the host application. Automation, undo, cables on the back, pattern lanes, browsing patches, music hardware integration and much more—it's all handled by Reason.

Develop What Matters

With the Rack Extension technology, we have taken care of the mundane household tasks, so that you can focus on what matters: your product idea. Leave it to us to take care of file handling, automation, undo, music hardware integration and more.

Your Products. Direct to Market.

Distribute your Rack Extensions in the Reason Studios Shop, direct to all your customers. Reason Studios takes care of downloads, updates, demo downloads, copy protection and credit card processing for you—the works!

"As a very small company with limited resources, we are able to focus our attention on new ideas without being encumbered with the details of supporting various operating systems and plugin formats."

Kurt Kurasaki, Peff

Tools for the job

  • API and Code Library

    The SDK comes with a library of useful code for Rack Extension development, such as FFT, memory handling, undo, sandbox, routing and communication with the Rack Extension host.

  • Recon

    Recon is used to test and debug your Rack Extension project. It's a test bench version of Reason based on Reason Intro that lets you load and run your prototype Rack Extensions and test it with Reason’s workflow, devices, other Rack Extensions and VSTs.

  • LLVM Compiler

    With the LLVM compiler, you compile your C++ code to bitcode that is used to build the Rack Extension. It's the compiled bitcode that is uploaded along with your Rack Extension's other resources to Reason Studios' automated build system.

  • GUI Design

    Design your Rack Extensions as you choose. RE2D lets you create 2D, high-resolution user interfaces for your products and convert to Reason’s format. The Rack Extension Designer (RED) 3D design tool is also available, though no longer the preferred format. In this tool you lay out and preview a 3D graphical interface. If you prefer to work in 3D, you can then convert your 3D GUI to RE2D format.

  • Parts Library

    As an alternative to creating your own GUI objects, more than 100 interface parts such as knobs, buttons, faders and display objects are supplied in the Parts Library. Each object can be customized to adjust properties such as color, texture, and more. This is available for both 2D and 3D GUIs.

Turn content into instruments

Do you sit on the idea for an amazing Rack Extension instrument, but don’t speak the language of DSP? Are you apt at building sample libraries? Then IDT2 is for you!

IDT2 is a development toolkit that allows you to create high-quality synthesis- and sample based Rack Extension instruments without advanced coding knowledge. Build anything from big string libraries to vintage-style synthesizers using the UJAM Gorilla Editor and an entire array of tools and scripts from UJAM Gorilla Engine, including 70 premium effects, filters, modulators, oscillators and sequencers. Your great idea just got a lot closer to a finished product in the Reason Studios Shop!

IDT2 was introduced in version 3 of the Rack Extension SDK. UJAM Gorilla Engine and Gorilla Editor are developed by UJAM.

Support from start to finish

Help is there when you need it. We are as eager as you to see your projects finished and will always be there to help you out.

  • Developer Community

    There is nothing like learning from your peers. As a Rack Extension developer you’re granted access to the Rack Extension developer forum — a lively and active community of developers. Check out the collection of stickies full of helpful tips to get started.

  • Testing

    Testing is of course essential to a quality product release. The developer section of the our web site gives you access to beta testing tools to help you distribute beta licenses to your testers.

  • Tutorials

    The SDK comes with ten written tutorials with code and scripting examples that will help you along the process from initial design to finished product.

  • Example Projects

    To dip your feet in the Rack Extension technology, we have supplied three straightforward example projects that will show how to create a simple instrument, a simple effect unit and a device with a custom display.

  • Reason Studios Support

    For help and assistance, we are always available to help you out. Our staff can help and guide you with issues related to development, administration or sales issues.

Beyond Rack Extensions

Aside from Rack Extensions, Reason Studios offer several de facto industry standard technologies for developers to use.


ReWire is system for streaming audio from one application to another. Pioneered in Reason Studios' ReBirth, it is now supported in every major DAW on the planet. The API, which is written in ANSI C, also has support for play positioning information, MIDI streaming and a toolkit for communication between the applications.


The REX file format allows for free manipulation of timing and feel within a sampled groove. A REX file contains the original audio of the loop, the slices you have applied in ReCycle, and any effects or processing you have added in ReCycle. REX files are also compressed, using a non-lossy compression technique to save some precious hard drive space. The REX format has been implanted in just about any DAW or software sampler out there.


Remote is a protocol for handling communication between control surfaces (MIDI keyboards, remote control devices, etc.) and software applications (e.g. Reason). It handles everything from delivering MIDI note data from a keyboard to the application to using knobs, faders and buttons on a control surface for tweaking synth parameters in the application, controlling transport, etc. Remote also supports two-way communication, in order to make use of motor faders, dynamic displays and LEDs.


NN-XT is the flagship sampler in the Reason Rack. A fully featured sampling instrument, it comes with everything needed to build rich and natural sounding sample patches. The NN-XT file format is open to third party developers to allow external applications to create NN-XT patches.

About Reason Studios

Formed in 1994, Reason Studios is a privately owned company based in Stockholm, Sweden. Renowned for its musician-centric approach, Reason Studios has created some of the world's most innovative music desktop software applications, mobile apps and technology standards. Musicians, producers and the media have praised Figure, Reason, ReCycle and ReBirth applications for being inspiring, great sounding and of impeccable quality. Technologies such as ReWire and the REX file format are de-facto industry standards, implemented in all major music software. Today, Reason Studios' products are used all over the world by hundreds of thousands of professionals and enthusiasts for all kinds of music making.

Ask us anything!

Got more questions? Ask us and we'll do our very best to help you out!

How to become a Reason Studios developer

1 Register your company

Sign up for a Reason Studios user account and register your company with us.

Create an account Register your company

2 Get the tools

We’ll review and approve your registration. Then download the SDK and get your creativity going

3 Build and submit your Rack Extension

Design, build, and test your Rack Extension. When it's ready, submit it for sale in our shop.

Who can sign up?

Anyone can register as a developer, but only companies can sell Rack Extensions or ReFills in the Reason Studios Shop. The requirements for selling products in our shop are:

  • You need a company with some sort of Tax ID, being a sole proprietor is sufficient as long as you are registered for VAT.
  • You need a website.
  • You need an email address where customer can get product support.

This means each developer will sign up for a user account and then apply to register a new company. If you don’t have a company yet, you can put your own name in the company name field.

If you want to be included in a previously registered company, send an email to that company and ask them to add you as a developer.

There are no costs involved. Reason Studios will administer the authorization, copyrights, logos, and trademarks. We’ll also provide technical support, free of charge.