*.OGG

.OGG is a container format for compressed multimedia files (OGG file format), and a popular competitor to .MP3. Usually it contains lossy compressed audio data (Vorbis) and/or Theora video data. Unlike MP3, Vorbis is an open-source, open-standard format with a permissive license, both of which allow it to be incorporated into the FS2_Open source code. Also unlike .MP3, .OGG can contain video (Theora) in addition to audio (Vorbis) data.

Since .OGG, as a lossy compressed format, delivers significantly smaller file sizes than .WAV, while retaining a high level of audio quality, it is becoming more and more frequently used in FSO-targeted mods.

Audacity and Goldwave are two popular programs that allow .WAV files to be converted to Vorbis.