This module is actually two projects, a general playlist
relationship API, and an audio_playlist.module which makes use of the
API.
Audio_playlist.module
This module makes use of the playlist.module API. It is a simple
node module that defines a new playlist node type called "audio
playlist". This name can be changed, however, to podcast, album, or
similar on the module's settings page.
Podcast (RSS), XSPF, PLS, and M3U feed generation is taken care by this module.
Features:
1) iTunes podcast/xspf/m3u/pls feeds generated on the fly, with full metadata support
2) album artwork can now be integrated (through URL)
3) xspf flash players for each feed, including popup players for each
4) audio browser, similar to iTunes, used to search audio tags and find the audio to add to playlists
5) upload new audio files to playlists on the fly with an inline uploader
6) listening station: an xspf flash player block that has a dropdown select to listen to different playlists on the site
7) Cut n' paste HTML and javascript includes for integrating the flash player on other sites
8) lots of customization options
Playlist.module
Seeking to generalize the functionality of all playlists, a common
toolkit will hopefully make it easy to build new playlist modules by
re-using common code.
The playlist.module provides:
database schema that can be used by multiple playlist types.
modules 
