aubio is a library for audio labelling. Features include onset detection, silence detection, beat tracking, and pitch detection. The goal of this project is to provide automatic labelling features to other audio software projects. Functions can be used offline in sound editors and software samplers, or online in audio effects and virtual instruments.
Tao is a software package for sound synthesis using physical models. It provides a virtual acoustic material constructed from masses and springs, which can be used as the basis for building quite complex virtual musical instruments. It comes with a synthesis language for creating and playing instruments and a C++ API for those who would like to use it as an object library.