My ears always prick up when music is mentioned.
Speaking as the resident classical musician in this cohort (any others?), I’d like to question your assertion that contemporary (by which I presume you mean avant guarde) music does not follow any rules and is thus a form of post-positivism.
I would argue, rather, that avant guarde music recognises the traditionalist rules directly and attempts to create new and different structures precisely in antithesis to traditional mores. This position is predicated on a deep knowledge and awareness of the rules. In a very practical (i.e. the power of the music in the intellect) sense, avant guarde only works because of the very rigidly and historically steeped rules that it tries to break. Another way of putting this is that some lauded work is new only in contrast with the old. A piece can only be challenging, exciting, interesting if we know what it’s not doing. A key term here is subversive.
You may spot an irony in the works, say, of Webern or Schoenberg who created very rigid and structured rules with which to create their avant guarde music (atonalism). That was 100 years ago. Schoenberg was reacting to the major/ minor tonality only. They retained aspects of rhythm, timbre, concept of space and so on. More modern composers have tried to break down each of these aspects. You will know the famous example of John Cage who ‘wrote’ a piece called 4’33” which comprises three movements of silence. Here is not the forum to discuss this, but I want to make the point that rather than not having any rules, contemporary avant guarde music most certainly does have rules. Just they are the proverbial elephants in the room.
Please allow me to correct a common misconception. Until very recently, avant guarde composers’ need for beauty, connection to the audience, personal expression and so on were very much in the background if at all. I remember in the 80s and 90s going to such events and talking with the composers afterwards, it was clear that such attitudes were frowned upon. The prevailing attitude was: My music is inspired intellectually, not by some base concern as popularity or inter-human connection.
 It is only ironic if the starting point is that the music should be rule-free rather than rule-bound. Early 20th century composers had no intention of breaking the rules. They tried only to undermine major/ minor tonality.
 Since 1948, there has been more ink spilt on the meaning of Cage’s silence that would fill a concert hall.