I did a little research and would like to present you with a short course on using your own music in BF1942, BFV, and mods.
Music is used in the main menu of BF1942 & BFV, as well as most mods have their own custom menu music. BFV also introduced vehicle music. Finally, maps themselves can have custom loadup music, but I believe this requires scripting/editing of .con files (any of the BIG guys can elaborate on this?), so I'll only cover menu music and vehicle music.
Music files in BF1942 & BFV are (if default) located in C:\Program Files\EA GAMES\Battlefield xxx\Mods\bfxxx\Music
If you look in those folders, you will notice BIK files. What on earth are BIK files? BIK is an video+audio file specification of RAD Game Tools. They specialize in video & audio for games only, and thus were selected by DICE to provide the video & audio sequences. What does this mean for you?
Tools you will need:
Audio editor - If you want to do some custom editing of your music, such as cropping and looping, before putting it into Battlefield, you will need an audio editor. If you don't already have one, get this one because it is good and better than that it is free http://audacity.sourceforge.net/windows.php
MP3 to WAV converter - In case you are using MP3 files and your audio editor doesn't convert MP3 to WAV, then use dBpowerAmp, it's very nice and also free http://www.dbpoweramp.com/dmc.htm
RAD Video Tools - This is necessary to turn your WAV's into BIK files http://www.radgametools.com/bnkdown.htm
1. Once you have edited your music file to your liking, you will need to save/convert to WAV format.
2. Open the RAD Video Tools. Browse to your WAV file. Hit the "BINK IT" button. Browse to a folder you would like to save the output file. The video options are not important. The "Compress Audio" should be selected. The only option required is compression level. I used 0 and it compressed a 30MB WAV file to 5MB with no discernable difference.
3. (Optional if needed) Backup the existing BIK files. If you are going to replace the DICE music files, you'll probably want to backup the original files. Some mods may not even have music files, so this won't be necessary.
4. Change the names and move the BIK file(s) to the music folder of BF1942, BFV, or mod. You will need to use the default names for BF1942 or BFV respectively. ** By placing in music in mod folders, you can customize music for different mods **
5. For BFV vehicle music, it is also in the same folder. ** This can also be customized per mod, by using the mod/music folder and default BFV names **
Hope this helps. If anyone has something to add, please post it!
Enjoy the music freedom of the Battlefield