STK

The STK software is an incredible tool designed for developing music synthesis and audio processing software. It prioritizes cross-platform functionality, realtime control, ease of use, and offers educational example code. Its portability is unmatched as it consists mostly of platform-independent C and C++ code. The best part is that it's user-extensible and offers all source codes with no unusual libraries or hidden drivers.

Since the STK software offers realtime support for both audio and MIDI, it can run seamlessly on Mac OS X, Linux, and Windows platforms. Additionally, it supports generic, non-realtime functionality, making it a perfect choice for NeXTStep, Sun, and other platforms. Standard C++ allows the software to work with almost any platform.

Overall, the Synthesis ToolKit is a fantastic software program that is free for non-commercial use. Whether you're a beginner or an experienced developer, this tool is perfect for working on music synthesis and audio processing software. Plus, it offers several features that can make your development work more accessible and efficient, and the included example code is an excellent resource to improve your knowledge of the software.