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a2jmidid is daemon for exposing legacy ALSA sequencer applications in JACK MIDI systems.

Equivalent functionality is now built into JACK 1. If you want to expose similar functionality using JACK 2 you will still need to use a2jmidid.

If you are using JACK 2, you can access this functionality by typing 'a2jmidid -e' into a terminal. You can set this to autostart when using a program such as Qjackctl by going to Setup > Options and adding 'a2jmidid -e &' as a startup script.