Hey @Jim_Austin,
@ncpl’s question is really the right one.
Many of us keep our media organized into neat folders, one per album/disc, but many don’t and we see a surprising number of “grab bag” folders, where multiple albums are in a single folder. We can’t assume a folder is the same as an album without having all sorts of unpredictable results.
The rules laid out here are really the most important – based on your description of this set, I’m guessing the album title fields weren’t the same, which will almost always keep discs from being automatically grouped together in a single album. If you think your media followed those rules and was still not grouped, let me know and I can take a look at the files. I’d be interested to know what went wrong.
We are considering expanded support for disc-level information, as we’ve heard requests for cover art or album titles within a multi-disc set. I can’t make a commitment here yet, but we are aware of this request. We also have a fully redesigned “track grouping” editor coming soon in 1.2, which should make it really easy to organize 9 discs into a single set in the correct order.