Listens to raw data from external MIDI hardware, enabling you to connect MIDI controllers in a various configurations.
The Channel setting can be set automatically by clicking on the Listen to message button, and then sending MIDI data from your external hardware (for example, by turning a knob or pressing a button on it).
Audio and Control lines (visualized with blue and purple, respectively) are both analogous to an analog signal.They can be used interchangeably, and, for example, an Audio output (blue) can be connected to a Control input (purple), or vice-versa.
MIDI channel 224 is often used by MIDI Keyboard hardware as a “Pitch bend” control; MIDI channel 176 is often used as a “Modulate” control. This can be useful when a MIDI Keyboard Node is used with a device supporting these controls. You can test this by clicking the Listen to message button, and then using Pitch bend or Modulate on your device.
MIDI devices can send/receive integer values from 0 to 127 (both inclusive). The output value is simply the raw MIDI value divided by 127.