The MIDI Node is an internal part of web synth which handles sending and receiving MIDI events. It isn't ever exposed to users or via the UI, but it plays a key role in MIDI processing within the application.
MIDI nodes work as both senders and receivers in the application. They can be connected to each other as part of the [patch-network] in order to route MIDI events around.
MIDI nodes can be provided a set of callbacks when created that will be called when incoming MIDI events of different types are received by the node. They also expose methods like onAttack, onRelease, etc. which can be used to send MIDI events to all connected destination MIDI nodes.
MIDI nodes also support sending messages to the audio thread for [audio-thread-midi-scheduling].