This question is an exact duplicate of:
On WP7, double albums (with two discs) all appeared under the same album, and were properly sorted by disc.
On WP8 they aren't sorted by disc but like: D2-1, D1-1, D2-2, D1-2...D2-n, D1-n.
I tried moving them to different folders, but this creates different folders in the music app as well.
Is there a way to get them all under one folder and properly sorted by disc?
The tags are correct as far as album name and track & disc numbers.