There is only one file type that uses the .MUSX extension:
Finale Notation File
A MUSX file is a notation file saved in MIDI format and created by Finale, a music notation program. It contains music notation data and additional information that can only be read by MakeMusic software. MUSX files replaced .MUS files.
To create a MUSX file simply selectwith your document open, choose your save location, name the file, select the MUSX file type, and click .
NOTE: The MUSX extension was introduced in Finale 2014.
Updated: March 18, 2018