define the TAG to display

[BiozTech]

I use Foobar2000 (it's my Swiss knife)

For treatment by batch, I tried Metatogger which is amayzing and freeware
http://www.luminescence-software.org

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Regarding my second question, I found the way using the tag together <DISCSUBTITLE>, <DISC NUMBER> and <TOTAL DISC> .
Minimserver show directories in the tracks list, for instance "original album" and "remixes" depending of the variables freely applied