Matching Lookup data with tracks, using Freedb and/or YADB
and mixing that data together, and updating the servers.
MC looks great and I've been playing with it all day, comparing it to some other tools as I organize a large audio library.
However, the way it works for lookups is (uncharacteristically) simplistic.
One of the tools I've been testing is
http://www.wensoftware.com/MusicLibrary/Here's an example of the kind of thing that I think might work better, while still allowing proprietary databases to grow.
Let's say we could use a lookup tool that does multiple lookups (shows tabs for YADB, Freedb and others), presents the user with options and allows track and album mapping in various ways before committing the changes to the database and writing the mp3 tags.
Basically your selected tracks could come up on a right-side list, underneath search fields (which should probably default to the current album or artist, if known)
Above that, there could be three tabs, one for YADB, one for Freedb searches, plus other databases under other tabs (AllMusic would be good for webpage reference.) Selecting these tabs allows the search fields to get different results.
The lookup search results produce a list of albums (or tracks.) Double click on one of the items in the list, and the track(s) from that item then fill the left-side fields next to the mp3 tracks you have already selected from your collection in the right-side fields. You can re-sort the right side list, re-order it by moving tracks up or down, match them to the left side tracks by manually clicking or by matching all strings in the titles or by matched track order. You can exclude selected fields from being replaced. You can go back to your lookup-search results list, to try out a different entry that may better suit your preferences (nicer English, better nomenclature, whatever).
When happy, click the commit button and this does what you've set up in the options, for example:
-writing id3 tags with the new info
-updating YADB with the info (this could be especially useful since the data may now be a mix of different databases plus previous user edits and entered data.)
-running the MC file renamer with its template