.MSCX File Extension

The standard save format MuseScore uses to save scores is the MuseScore Compressed Score ( .MSCZ ) format. When you save a score in the is format (by selecting File → Save , MuseScore creates an MSCX file to store the score, and Zip compresses it as an MSCZ file along with other resource files, such as .JSON files and .PNG thumbnails.

NOTE: MuseScore introduced MSCX files in version 0.9.5 due to a file association conflict in Windows. Earlier MuseScore versions use the .MSC file extension.

To open a .mscx file, you need compatible software that supports this file format.