File extension: MUS File type: Music Notation File. The MUS file type is primarily associated with ‘SCORE Music Publishing System’ by San Andreas Press. The SCORE music printing system is intended to facilitate the creation of virtually any page of standard music notation with a final quality equal to that of true engraving. Most of the shapes used in music printing are found in the SCORE drawing library. Any unusual musical symbols may be added to the library. Primary association: SCORE Music Publishing System Company: San Andreas Press Related links: Score Preview: A Viewer for Score Music Files