Since there was an earlier discussion on how to store digital audio on servers, as well as this discussion on the CD audio file format, let me point you to a clear explanation of Microsoft on the evolution of WAV and RIFF to ASF (an advanced so-called presentation format). This format, used by the MediaPlayer framework, includes MPEG (and thus MP3), and allows one to embed metadata (or tags) "into" the audio (and video), so that it may be displayed on the client's screen as the contents play (streamed or locally). The ID3 tag allows for any kind of metadata. The Microsoft audio encoder allows one to fill a preset list of metadata as well as create new ones. The Microsoft explanation (only the caption is in German, the rest is in English): http://www.hit.fh-karlsruhe.de/windowsmedia/asf.htm About ID3: http://www.id3.org/intro.html Michael Fingerhut