CIOS Audio Core is the infrastructure and subsystem in Collective Intelligence Operation System. It is a cross platforms audio abstract interface, supports including Mac OS X, Linux, Android, iPhone OS and Windows 7.
TappedAudio is an audio library with an emphasis on the programming interface -- agnostic to the backend, written in highly-encapsulated C++ and using SWIG to present a unified API for C++, Python, Ruby, etc., regardless of the underlying audio platform.
Tinara is a media production system, currently composed of a basic revision control and archival system (DaMarcus), a build system (Alice), an audio playback engine (Tape), and a graphical audio recording and editing application.
Visecas is a graphical user interface (GTK+) for Ecasound (http://eca.cx/ecasound), a software package written by Kai Vehmanen (k@eca.cx) which is designed for multitrack audio processing.