Raul (Realtime Audio Utility Library) is a C++ utility library primarily aimed at audio/musical applications.
It is used by Ingen, Patchage, and Machina.
Download
The latest version of Raul is 0.5.0.
Experimental Debian packages are also available (or can be built from source with make deb)
Development
The most recent development version of the code can be checked out of SVN at http://svn.drobilla.net/lad/raul.
Chances are if you want Raul you want to check out the complete repository:
svn co http://svn.drobilla.net/lad
Development of Raul can be tracked here (change history, bug reports, etc).
Documentation
Bugs
Please file any Raul bugs you find here