Current questions and answers regarding the map editor.

Already existing

Okay. So, when you click on a music file, there's a "FileName" field, which is the file path (for most people, it's ..\Music\AI-Themes\AITheme-Haven.ogg). Let's say you want them to have the Renegades theme; then you need to change this path to the Renegades music (..\Music\a1\AITheme-Renegade.ogg).

Added 4 minutes later
Again, you can find this in the same window (where you looked for the music), but it's called "Sound."