Before I go in: I am Korean and this is my first time posting on the LFS forum. I am not good at English so I used a translator so my grammar and sentence choices may be awkward. Please understand

I want to play LFS while listening to Eurobeat, but there are ads when I listen to it on YouTube, so I want to add songs as MP3 files and listen to them. Is there a way to solve this?

You can play music in LFS, but files need to be in Ogg format.

They should be added to ./data/ogg directory.

When in game, SHIFT O and then click on Audio, where there's a small section for music.

I recommend just using an Adblocker and listening from YouTube directly. uBlock Origin is great, I also recommend using Mozilla Firefox or Brave browsers

How about you play your favourit mp3's in winamp? oldschool style

Quote from rane_nbg :

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If we go even further:
I recommend to learn all of your favorite songs and whistle them while driving/playing on LFS!

You can get a free audio converter such as AVS Audio Converter, import your favorite songs and choose the .OGG button and export your music into LFS\data\ogg folder.

After starting up LFS, go to the Options/Audio and click the Channels button down on the right. There, you can create a new playlist by clicking the New button on the left and give it the name you want. The button NEW below the screen will be used to create a space to import the song you want and the button NAME next to it will be used to choose the song from the OGG folder.
The different columns are for different context such as the Game Menu, Race, Replay. The Channel 1 is the menu. If you do not want a specific song to play in race and just for the menu, you do not add a number on the RACE channels, only on the MENU one.

You can create different playlists for racing such as a playlist of Electronics or another for something Rock etc.. A higher value will have a song play more often when you are in shuffle mode.