Cross-platform Audio Creation Tool (XACT) is an audio programming library and engine released by Microsoft as part of the DirectX SDK. It is a high-level audio library for authoring/playing audio that is written to use Xaudio on the Xbox, DirectSound on Windows XP, and the new audio stack on Windows Vista and Windows 7. Xaudio is an Xbox-only API designed for optimal digital signal processing. XACT also includes X3DAudio, a spatialization helper library available on both platforms, Windows and the Xbox. XACT was originally developed for Xbox development, and was later modified to work for Microsoft Windows development as well.