Obviously the first part of doing it is to get the .mp3 or .wav. When this is all done the format will be .wav because that is the format l4d2 requires.

Step 1: You will have to get the audio you want to replace. It can be any format you want it to be at first but it will be converted to .wav later.

This part is very important because you cannot just convert the audio to .wav and be done with it. You need to set it to a specific sample rate, sample size, and channel. If you don't the audio will sound a bit slow or fast in-game.

Step 2: First of all your going to need to download the software that is going to convert the audio into a usable format and rate. It is called dbpoweramp. It is not free though but you can use this or find another program that is a complex as this. I PROMISE you this is the only thing your going to need to download in this tutorial!

Link: http://dbpoweramp-music-converter.en.softonic.com/download

Step 3: When you have dBpoweramp downloaded and installed either right click on the file you want to convert and click Convert to... in the list of options or open up dbpoweramp and it will bring you to windows explorer where you can simply double click on the audio you want to convert.

Step 4: Set converting to: as wave

Step 5: make sure to check the box Uncompressed then fill in the boxes with these

*IMPORTANT UPDATE* : It seems that a lot of audio files use a format that is different from this rate. If so, find the original file you are replacing, right click on it and chooce "Properties", go to the "Details" and you will find these settings there. Use THOSE settings, not the ones I give.

*UPDATE #2* : It seem that thanks to the magic of Windows 10, the Details tab doesn't give you these settings. Just follow these instructions.

For Music Converstions:

Channels: 2 'stereo' (CD)
Sample Size: 16 bit (CD)
Sample Rate: 44.1 KHz (CD)

For Voice Converstions:

Channels: 1 (mono)
Sample Size: 16 bit (CD)
Sample Rate: 44.1 KHz (CD)

NOTE: These are the most common used rates for music files in l4d2. These may change depending on what you are doing. In which case go to the original audio file in your left4dead2 sound foldier and right click on the file then go to properties. Then click on the tab called "Audio Properties" to view what these should be filled in as.

Step 6: Set the output foldier to where you would like. Either to the original foldier or another foldier of your choice then Convert >> at the bottom of the window.

This is where it all comes down. After you have the audio converted this is what you do with it.

Step 7: Go to the place where the original audio file (the one you want to replace) is stored.

Step 8: Copy and paste the new converted audio file into the foldier.

Step 9: You are going to want to take note of the name of the ORIGINAL audio file. Write it down somewhere or just memorize it. You have to memorize it EXCATLY the way it is meaning if the first letter of the name is lower case keep it that way.

Example:

left4death (original)
The end of the battle (new one)

Step 10: Rename the new audio file as the SAME name as the original file. This will make it so the game knows what song is being replaced.

Step 11: It will probably say that there is already a file with that name in the foldier. THAT IS FINE. Just click on the option to RENAME BUT KEEP BOTH FILES. It will then add a (2) at the end of the new audio file.

Example:

left4death (original)
left4death (2) (new one)

Step 12: Take the original audio file out of the foldier and put it somewhere safe in case you want to put it back.

Step 13: Now there should only be the new audio file with the name of the song you want replaced in there (the one with the (2) at the end). Rename it again only delete the (2) and the space between it and the name.

Example:

left4death (2) (new one)

And your done! In the end the foldier should look like it has the EXCACT same files as before only the original only that the sound in one of the audio files should be different. Go into the game and test out the new audio file.

I have now uploaded a guide which will show you both how to turn these sound mods into .vpk mods, AND how to upload them to the workshop if desired.

Find it here:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=398938698