JUCE

JUCE, short for Jules Utility Class Extensions, delivers a powerful C++ framework that can set the base of robust audio applications, plugins, and libraries. The framework is designed to work with all the major platforms, providing support for Windows, Mac OS, and Linux altogether.
The JUCE toolkit encompasses everything you need to build appealing GUIs for your app, delivering audio processing functions, modules and classes, MIDI support components, libraries for audio and graphics, and much more. It encloses the essential programming tools required for developing high-quality and appealing music software solutions.
The download only includes the framework and its components but, alongside it, the JUCE project includes a versatile project management tool that goes by the name of Projucer. With its help, C++ developers can generate various types of projects, including animated, OpenGL and console apps, static or dynamic libraries, or audio plugins. Its list of target IDEs includes Visual Studio or Code::Blocks on Windows, Linux Makefile, Android Studio or Xcode on Mac and iOS.
The JUCE framework includes classes and modules for audio processing, devices and formats, cryptography, data structures, video playback and recording, and more. Not only that it can successfully handle the audio processing part, but it is also suited for the creation of custom interfaces for the app.