.MUI File Extension

File Type 1

Myriad User Instrument File

Developer Myriad Software
4.1  |  504 Votes
Category Audio Files
Format N/A

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.

More Information
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

Updated May 25, 2022
File Type 2

Multilingual User Interface File

Developer Microsoft
4.0  |  246 Votes
Category System Files
Format Binary

What is a MUI file?

Resource file used by the Multilingual User Interface component of Windows 2000 and later; contains resources that allow the Windows interface to be changed to different languages.

More Information

Many MUI files can be found within the Windows %SystemRoot%\​ directory (e.g., %SystemRoot%\​en-US\​ in Windows 7). They may also be located within specific program installations, such as Windows Journal, Windows Defender, Windows Mail, and other Microsoft Windows programs, including Notepad (notepad.exe.mui).

Additional language packs can be installed in Windows 7 by selecting Control Panel → Clock, Language, and Region → Change display language → Keyboards and Languages and clicking the Install/uninstall languages... button.

Programs that open or reference MUI files

Updated July 1, 2010

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