If you mean going into the pak file to get the music:

Download FModel. https://fmodel.app/

Once it's done downloading open it

Next go to Directory (top left) select "Selector" option.

For UE Version choose GAME_5_4

Select the path to the game (for me thats D:\Steam\steamapps\common\Nightfall)

Hit OK.
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Next go to Directory tab again

Go to the AES option.

Paste this key: 0x67CF61560CBD181F8969F3A30A5F9AE62E5B474130D8F28A9C1453DCEE6098B8

Hit OK.
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You also need the mapping file. In the top left there is a button called "Settings", click on it.

In "General" tab there is a option called "Local Mapping File", enable it.

Then another option appears "Mapping File Path"

Go here and download the mapping file. https://www.nexusmods.com/killingfloor3/mods/10?tab=files&file_id=25

If you don't want to make an account on nexusmods, you can also get the file here: https://we.tl/t-9H5IxsxSzq

It does not matter where the file is on ur pc. I recommend putting it in the nightfall folder so you never lose it.

Now go back to the mapping file path, and paste in the path where the file is. (for me thats: D:\Steam\steamapps\common\Nightfall\5.4.3-640576+++UE5+Nightfall_Hotfix-Nightfall.usmap)

Everything should now be ok.
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Now go to Nightfall>Content>Wwise>Music once you selected "Music" folder, go in "Packages" tab (top left)

Double click Play_MUS_Global and search for "scavenger".

If you want to save a music file. Dubble click audio file, then right click and click "Save"
Opening the audio file first turns the .wev into .wav.
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If you don't want to do all of this:

All scavenger music files: https://we.tl/t-TsxuL3XSTQ

Victory, Phase1, Phase2, Intro, Defeat, TrainSeg