The most reliable, accurate, and completely free way to convert an MSCZ file to MIDI is by using the official MuseScore desktop application. Because MuseScore natively understands the MSCZ format, this method ensures no data is lost or corrupted during export.
Save as convert_mscz_to_midi.bat (Windows) or .sh (Mac/Linux): convert mscz to midi
If your MuseScore file has tempo markings (e.g., Allegro, Ritardando), these are generally embedded into the MIDI clock data. The most reliable, accurate, and completely free way