What is the etiquette here? Edit the existing record to be the full release? Add just the first disc? Add the whole release? It just really stumped me.
The first thing to check is that the release in question is not simply a different edition that contains only the 2nd disc. We can look at the edit history to see that no such information was indicated in the edit note, this just came from a freedb import back in 2005, so it’s probably fair to say that this release is simply missing the first disc.
So indeed, you should edit this release to add the missing first disc.
On the tracklist tab of the release editor, select “Add Medium” near the bottom, enter the tracklist, and then use the up/down arrows to order the discs correctly.
Also you should presumably remove (disc 2) from the release title while you are editing this.
It’s not uncommon: I have ran into a similar situation while adding my collection. Interestingly, this also concerned an import from freedb. In my case, I’ve added the missing disc as a separate release and then merged the releases using the “append medium” strategy.
For the record, the first disc here was originally submitted at the same time to MB but was unfortunately voted down (from original editor edit history):