.MUI File Extension

Myriad User Instrument File

Developer Myriad Software
4.1  |  532 Votes

What is a MUI file?

An MUI file contains a user instrument created by Myriad Harmony Assistant. It stores sound data for an instrument such as a piano, guitar, clarinet, or trumpet. MUI files are used for generating realistic sounds.

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Screenshot of a .mui file in Myriad Harmony Assistant
MUI file open in Myriad Harmony Assistant

Harmony Assistant comes packaged with many default instruments saved in MUI files. Each instrument file consists of a recording of an instrument playing a specific note and parameters to tell the program how it should be played.

In Harmony Assistant, you can create instruments other than the default ones packaged with the software by editing an instrument and selecting Save predefined instrument in the Action contextual menu. You can also define the parameters of the instruments such as the note range, sound attack rate, decay, volume release, and loop release.

How to open a MUI file

You can only open an MUI file with Myriad Harmony Assistant. The software is available for Windows, macOS, and LInux.

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Programs that open MUI files


Multilingual User Interface File

Developer Microsoft
4.0  |  250 Votes

A MUI file may also be a resource file used by Windows' Multilingual User Interface component. It contains resources that allow Windows and various programs' user interfaces (UI) to appear in different languages. Windows 2000 and later versions use MUI files.

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Windows' Multilingual User Interface (MUI) is a localization feature that allows users to set the operating system and many applications to use a different default language. This feature uses MUI files, which contain system- and app-level localization resources.

You can find MUI files within various Windows system directories, such as sub-directories of ~/​Windows/​WinSxS and ~/​Windows/​System32. You may also find MUI files within program-specific directories, such as the directories that contain Windows Defender and Microsoft Notepad.

How to open a MUI file

MUI files are not meant to be opened.

Programs that open or reference MUI files

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