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What is a .musx file?

A .musx file is an Archimedes Tracker Module. This one is a specialist format without an obvious everyday home. Confusingly, this extension has been used by 2 different formats over the years — they're all listed below.

This extension has been used by more than one format

2 different formats have claimed .musx over the years, so two files with the same extension aren't necessarily the same kind of thing.

How to open a .musx file

The program that created it is by far the most reliable way to open it.
On Windows, use a hex viewer or the free TrID tool to identify what the file really is.
On Mac or Linux, running `file yourfile` in the terminal identifies most formats instantly.

The registry records this extension against Archimedes Tracker Module, Finale Notation File, so software from that family is the most likely match.

How to convert a .musx file

Identify the file first, then look for an export or Save As option in whatever program can read it.

MIME type

When a .musx file travels over the web, servers label it with this MIME type:

application/vnd.makemusic.notation

What's a MIME type?

The technical record

For archivists, developers and the merely curious: these are the PRONOM registry entries for .musx.