The player itself is copied into client-side storage; it can be used without an active network connection.
Loaded MIDI tracks are copied into client-side storage; they can be played without an active network connection.
The MIDI tracks can carry a Device Name MIDI Meta Event which specifies the USB device name of the MIDI device to route the track's MIDI messages to. USB devices are recognized and automatically selected.
The MIDI file metadata can be edited with versioduo.com/edit.