You can readily find Linkin Park music anywhere in the market. You'll need it in digital form, even better if it's lossless so you can enjoy it more. You can easily find it on vinyl in the internet so you can just use a vinyl to .flac transformer and you'll have it ready to go.

First, go to your music settings:
Steam > Settings > Music
There you can specify a folder on your hard drive for Steam to scan for any supported music files. Once scanned they will be available in your music player.
Currently it supports MP3, FLAC, OGG Vorbis, and M4A (both AAC and Apple Lossless) files.

You can open the music player from the menu bar in the upper left corner of your Steam client:
View > Music Player

You can also find it by opening the Steam Overlay while playing a game. (by default: shift + tab)

There are several ways to achieve this:

• Silence the game via desktop settings.

If you are on Windows, you can open the volume mixer and silence Vacuum Pilot. Similar settings can be found on Mac and Linux devices.

• Silence the music in-game.

Open Vacuum Pilot and go to settings, and in the audio section you can lower the Music volume setting all the way to 0.