zynjacku (LV2 synth host, includes lv2rack) zynjacku is JACK based, GTK (2.x) host for LV2 synths. It has one JACK MIDI input port (routed to all hosted synths) and one (two for stereo synths) JACK audio output port per plugin. Such design provides multi-timbral sound by running several synth plugins. lv2rack is a host for LV2 effect plugins (like jack-rack is for LADSPA plugins).