Before beginning, you will need to have WinRAR and Audacity installed; and have file extensions shown.

Step 1. Firstly, you will need to go to the directory where you installed MWO.
By default it should be found in: C:\Program Files x86\Steam\steamapps\common\MechWarrior Online\

In the "Game" folder, scroll down until you find Music.pak












Step 2. Right click Music.pak and select "Open with..." then navigate to WinRAR.exe
After doing that, extract the "music" folder out of the .pak













Step 3. This is where you can modify the music files. Look through the music folder you just extracted and find the songs that you want to replace. In this example, I will be replacing the main menu music.

MWO uses .ogg format, so make sure that the songs are converted into .ogg
You can convert them through a program called Audacity.

Here I renamed the custom songs I chose, to the same names as the ones in the extracted folder. You don't have to rename the songs, however you will need to change the access directory in the .XML file that is found in the music folder.












Step 4. Right click the extracted music folder and select "Send to...", and select "Compressed (zipped) folder."















Step 5. Finally, rename the zipped music folder into anything as long as it starts with "z-". This is because MWO loads files from top to bottom and prioritises last loaded files.

After renaming the zip file, change it's extension from .zip to .pak and move it back into the "Game" folder.










Step 6. That's it!

If the default amount of music files are not enough to your likings, or there are too many, you can edit the .XML file in the music folder.

Adding more songs is as simple as copying the lines that are already there, and pasting another. Although, look out for where the line is as it determines what situation it'll be played in.

To tell when a line begins and ends, look for < >.

Using the copied line, change the "pattern name" to something unique, and change the directory of the song to the directory of your custom song. In this example, I am adding another battle song intro.

This process is not the same for replacing sound files (gun shots, foot steps, voices, etc). This appears to only work for music files. It may be because the devs left the music files open on purpose so that it would be easily modifiable.

It is possible to modify the sounds though, however you will need to download FMOD studio to open the .fsb files. I may or may not make a guide on this.

Also I cannot guarantee that this'll work on other operating systems other than Windows. As long as there is some kind of zip compression equivalent, the other steps should be unaffected.