Although I had already posted my ima2tun program >here, I've decided that a separate topic might be more easy to find.
This zip file contains my ima2tun program tunconverter, SoX, and some handy-dandy batch files that do all the command-line work.
To convert any* music file to .TUN/PCM, simply drag it onto the 'to-tun' batch file.
It then creates a .tun file with the same name in the same folder.
It's also possible to drag a .tun/.pcm file onto the 'from-tun or pcm' batch file to convert it to .ogg (filetype be changed in the batch file)
TUN files have a fixed sample rate of 22050Hz, but PCM files can have any sample rate.
The number of channels in a TUN/PCM file is either 1 or 2.
Preview: (old version)
Note: This download includes a copy of SoX 14.4.2, also available at http://sox.sourceforge.net/.
Is GameIntr.tun used in the game?