×1. Place the file, subsky.ogg, in the data/Music folder in the DROD root directory. Under Windows, this should be C:/Program Files/DROD - The City Beneath. Dunno if it works with JtRH, and Mac and Linux users are on your own.

2. You might need Ogg Vorbis codecs if you want DROD to play Ogg files, but I'm pretty sure all the sound effects in DROD are ogg encoded by default so it must have a decoder pre-installed. Just in case, or if you want to listen to it externally, you can get ogg codecs here.

3. Open up your drod.ini file in a text editor. It can be found under the data folder. Scroll down to where it says "[Music]".

4. Change the following lines:

FortressAttack=fortress aggr 1.ogg;fortress aggr 2.ogg

to

FortressAttack=subsky.ogg;fortress aggr 1.ogg;fortress aggr 2.ogg

and

FortressPuzzle=fortress cont 1.ogg;fortress cont 2.ogg

to

FortressPuzzle=subsky.ogg;fortress cont 1.ogg;fortress cont 2.ogg

This will change the music for the Fortress theme only, and still keep the original DROD music. If you want to change Deep Spaces too, put similar changes in the "Deep SpacesAttack" and "Deep SpacesPuzzle" lines.

5. Open up DROD and enjoy.

Note to Vista users: You have to run DROD under admin privileges in order for it to read out of drod.ini.