Beast is a music composition and modular synthesis application. beast-0.11.0 is now available at beast.testbit.eu. Support for Soundfont (.sf2) files has been added. On multicore CPUs, Beast now uses all cores for synthesis, which improves performance. Debian packages also have been added, so installation should be very easy on Debian-like systems. And as always, lots of other improvements and bug fixes went into Beast.
Update: I made a screencast of Beast which shows the basics.