I think that on this issue there is no much to inventThe idea is that all tracks have information assigned in the comments e.g. "rock, 80s, slow" and you select tracks based on the comment filter.

Here below I have attached several videos of other software on the subject. (Sorry for breaking the rules of the Forum but I think it is worth)
Current solution is very cumbersome, I am aware that change everything to database server would be hard work, but cannot be implemented categories and subcategories with a single XML?
Use the comment field for this is a bad idea in my opinion.
Another thing I really liked is to have customizable fields for the user, to store what the user precise (within the Tags of the tracks). (This idea was extracted from PowerGold)
In my case two things that would be very useful to store and filter I can think of: a track time (slow, medium, fast) and an additional rating but the moment in which the song was popular: for example the song "Crazy Frog - Axel F" in 2005 (the year of release), in rating at the time of launch would be 10. However if I had to put a current rating would be 1. Store this can be very useful, but other users may need another thing and with this not would have problems.
I'm open to opinions and ideas.