MIDI Options page sets MIDI parameters for current MIDI file. This dialog can be invoked from "Operations"->"Edit MIDI File Properties" menu item.
These options do not affect sounding of MIDI file at all; they rather affect some attributes of the MIDI file.
Copyright String - this is copyright string that is written to the MIDI file.
Key - you can assign any music key to the resulting MIDI sequence. It does not transpose the piece.
Meter - you can use this parameter to set the meter (2/4, 3/4, 3/8 and so on) of the MIDI file.
Tempo sets the tempo for the MIDI file.