DSSI (pronounced "dizzy") is an API for audio processing plugins, particularly useful for software synthesis plugins with user interfaces. DSSI is an open and well-documented specification developed for use in Linux audio applications, although portable to other platforms. It may be thought of as LADSPA-for-instruments, or something comparable to VSTi. This requires qt3 from extra/kde3-compat, ladspa_sdk, liblo, and jack.