Jack is an audio and midi connections tool. We will be using it to create and test connections between MIDI hardware devices and Virtual MIDI devices, and between Audio Channels and Audio Effects.
Creating Connections from your Hardware MIDI device to a Virtual MIDI device
Right click on the Jack Control icon on the bottom left side of the task bar
Select 'Connections' from the Jack Control menu that appears
The Connection screen will now show, and you will see three tabs indicating the three types of connections available - Audio, MIDI, and ALSA.
Note: ALSA stands for Advanced Linux Sound Architecture and that tab will contain all the installed hardware MIDI devices and the configured Virtual MIDI devices. The MIDI tab configures Jack MIDI ports which require specific software drivers with the application. Fluidsynth will be using ALSA MIDI ports by default and so these will only appear in the ALSA tab.
Click on the ALSA tab. You will see all the MIDI Out devices (those that are sending MIDI data) on the left had side, and all the MIDI In devices (those that are receiving MIDI data) on the right.
Click on the (+) node of one of the devices to expand the device node and show the available MIDI Ports
To connect a hardware MIDI keyboard to a virtual MID device and Port, click on the name of the MIDI device in the left hand column, then click on the Virtual MIDI device in the right hand column, and then click on the 'Connect' button
Modifying Connections
You can disconnect Jack connections and make new connects that suit your particular hardware setup.