The Neptune Project design document is pretty well underway. Expect it in a week or two.
The long discussed and slowly developed Neptune project is respawned now on SourceForge. Neptune's goals are a flexible MIDI/tracker/whatever else platform independent playback engine, plus a series of OS-specific frontends - GUI editors/trackers, players and conversion programs. One of the frontends for Linux is now being developed in parallel with main NTSE (NepTune Sound Engine) development - the Organik trakker (http://organik.sf.net).