Carla is a versatile audio plugin host, introduced in LMMS 1.1.
Carla hosts VST, LV2, DSSI and LADSPA plugins in a modular way, allowing you to chain synths, effects and controllers in a flexible environment.
Carla currently only works on Linux. Windows and OSX are not supported at the moment.
Rack and Patchbay
In the instrument menu, two Carla instruments should be available, named Carla Rack and Carla Patchbay.
In the Carla Rack instrument, loaded plugins will show up in a virtual rack as units with control buttons and VU-meters. The internal midi and audio routing is fixed in this mode, and goes from top to bottom.
In the Carla Patchbay instrument, plugins are loaded as units with inputs and outputs onto a canvas. Midi and audio can be routed anywhere to anywhere giving an enormous flexibility to this mode. Rack mode view is also available in the Patchbay instrument.