The Calf project aims at providing a set of high quality open source audio plugins for musicians. All the included plugins are designed to be used with multitrack software, as software replacement for instruments and guitar stomp boxes (and not as single modules in a modular synthesizer, which was a primary design goal in some other open source plugin packages[*]).

The plugins are available in following formats:

* LV2 (both synthesizers and effects; MIDI I/O and GUI extensions are supported, while presets are currently not); recommended hosts: Ardour 2.7, Zynjacku/LV2Rack.

Note: you need a *proper* version of libslv2, redland (librdf), raptor and rasqal for those programs to work correctly with Calf (live graphs and all). One "known good" combination is: libslv2 svn r1822 (probably r1799 or later), redland 1.0.8, raptor 1.4.18, rasqal 0.9.16. If you see live graphs in calfjackhost but not in LV2 hosts, try updating those libraries, it should help. Both Calf and SLV2 are "work in progress", and there may be occasional bugs.
* DSSI (both synthesizers and effects, GTK+ GUI is included)
* Standalone JACK client application with GTK+-based GUI (new: it is possible to run several plugins simultaneously in one JACK client, and connect them in chains using standard JACK facilities)
* LADSPA (only effect plugins, GUI not available unless host supports DSSI-style GUI for LADSPA), with LRDF. Note that use of LADSPA is strongly discouraged, as the limitations of the standard may cause serious inconvenience. Please use LV2 or DSSI instead, if available.

Due to limitations of plugin architectures, not all features may be available in all versions. The most feature-rich version is the standalone JACK client. However, it is expected that LV2 version will achieve maximum functionality as well, once all necessary LV2 extensions become mature. DSSI and LADSPA versions will probably not become as complete as LV2, due to serious restrictions imposed by those architectures and their status (practically obsolete).