jFonia is a framework/API for music, focusing on symbolical (discrete) data such as notes, clefs, measures etc.
It is a low level framework, aiming to facilitate the development of high level music software, such as score players, viewers, editors, analysis and composition tools etc.
Chords and lyrics For "Oh Mary Don't You Weep" (also known as "Mary Don't You Weep"), plus a recording and an explanation of this song's origins.
CLAM is a software framework for research and application development on the audio and music domain. It provides means to perform complex audio signal analysis, transformations and synthesis. It also provides a uniform interface to common tasks on audio applications such as accessing audio devices and audio files, thread safe communication with the user interface and DSP algorithms recombination and scaling.
You can use CLAM as a library to program your applications in C++ but you can also use graphical tools to build full applications without coding.