NOTE: The guide is partially outdated, mostly the images, the process is exactly the same though. Whenever you see something reference OldMusic.bank, look for ZomboidMusic.bank
I do not have a lot of interest in modding this game due to various reasons.

• Audacity[www.audacityteam.org] to edit your songs properly into the game!
  
• FMOD Bank Tools[www.nexusmods.com] to modify PZ's soundbanks!
  
• Your own songs of course!
  
• Project Zomboid's OldMusic.bank file! (or ZomboidMusic.bank)

You will also need to dedicate some clean work area for yourself like this:

MAKE SURE TO BACKUP THE ORIGINAL OLDMUSIC.BANK OR ZOMBOIDMUSIC.BANK IN CASE IF YOU SCREW SOMETHING UP

The soundbank is located in:
ProjectZomboid / media / sound / banks / Desktop
Here are some images to help you find the soundbank quickly:

Once you locate the Soundbank file, head back to your work area where you've put the FMOD tools in and open the folder called "banks" then copy the OldMusic.bank inside. example:

When it is done, you can go back to the main folder and open "Fmod Bank Tools.exe"
You will be met with a window like this:
All you have to do for now is to click the button called "Extract":
Once the extraction is complete, a confirmation window should appear.
You will be able to find your extracted soundtrack files in the "wav" folder:

To make management easy, you should create a folder in your workspace where you will save the modified soundtrack, in my case the new folder would be called "soundtrack":

(the folder's sole purpose will be to serve as an location where you will export the edited .wav's)

Let's go back to the folder with the extracted sound files and open one of them with Audacity, the easiest way to do is to simply drag and drop a sound file onto Audacity's gray area:


You can now edit the original soundtrack as you wish, but obviously the point of this guide is to replace it, isn't it?
Drag and drop the song you would wish to replace alone.wav with into Audacity, just like in the gif above. Here is a screenshot of two songs in a single Audacity project:


← You can now remove the original track from the project and here you go! Your song now replaces the original soundtrack! All you have to do now is to export it as .wav!

→ Here is how you export the file, make sure that you export it as wav with the same filename as the original!







You can export the file anywhere you want but it'd be most preferably to export it to the folder you created in your workspace, once again it would be in the folder called "soundtrack" in my case.
]

This is all the basics you need to edit your soundtracks, have fun and good luck!

Once you are done creating your custom soundtracks, you will most definetely have a folder full of those custom .wav files, the next step would simply be copying the all of those custom .wav files and pasting them into the folder with the original ones. Make sure that you overwrite all of the files!



Once that is done, go back to your FMOD Bank Tools and click the "Rebuild" button!


When rebuilding is done, go to the "bank" folder and you might notice that the OldMusic.bank has changed it's size!

Of course, the modified bank's size may vary for you!

You now have a functional modified soundbank that PZ can read, it's time to move the modified one back to where you got it from!


And here you are, your custom soundtrack is now in the game!

Simply change your Music Library to Official and Music Action Style to Legacy

• If your audio is looping or ending abruptly, you might have either used a track that is shorter or longer than the original track. Your custom track should end at the same time as the original one ends, fade in and fade out are your friends!
  
• If you screw up your .bank or lose the original .bank simply delete the broken one from PZ's directory and verify your game cache via the game's properties on Steam.

I have tried my best to make this guide as user friendly as possible, if there still any concerns or issues you may face please leave a comment or contact me directly.

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2282665384
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2350360114
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2392598601