Ok, there is really nothing special about chords, I guess. Using major chords and minor chords should be fine.
The thing that makes bulgarian music interesting is the usage of odd time signatures such as 5/8, 7/8, 9/8 etc.
Also, in some regions they sing in such a way that they make transitions in quarter tones. Example: lets say at some point the singer sings A and then she sings somewhere in between A and A#.
There are much to be said on the topic but I am not quite very well prepared to give you some more extended information. Ask me if you have any specific questions, I will try to answer.
By the way, why are you interested, I mean there should be some special reason, I guess, It does not happen everyday someone here to ask about Bulgarian music. Just curious...
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