Oddb411: To which game are you trying to add music? I I only have X-Wing and Tie Fighter, but I've managed to add custom music to both of them. For Tie Fighter I just used the Reconstructed Mod, but for X-Wing I put together some tracks from the Rogue Squadron games on my own and had no problem importing them.
For X-Wing (Windows version), the in-flight CD audio is by default in C:\GOG Games\STAR WARS - X-Wing (1998)\MUSIC, with Track02.ogg to Track08.ogg. You said that you used a converter to make OGG files, but did you rename them to "Track02.ogg" and "Track03.ogg," and so on? If you want to replace the songs, you have to make sure they're the exact same name, otherwise the game won't read them.
X-Wing also has other music for menus, transitions, and cutscenes, which are by default in C:\GOG Games\STAR WARS - X-Wing (1998)\XWINGCD. If you're replacing those, they have to be WAV files and also need to have the same names of the tracks they're replacing.
For Tie Fighter (Windows version), everything is in one folder, C:\GOG Games\Star Wars - TIE Fighter (1998)\MUSIC. Same thing applies there, convert in-flight music to OGG, cutscenes and transitions to WAV files, rename them exactly as the originals, and put them in the folder.
Ah ok, thank you. Im guessing that since its only track02-track08 that theres a 7 song limit. Oh well, thats a shame, theres so many wonderful songs in starwars.