conceptnet api documentation for /wn/ part of the URI
This is the finer-grained word sense information that was added in ConceptNet 5.7. WordNet defines "music" in the topic area of "communication". We keep this information in the word sense. The idea is to distinguish WordNet senses, but not to make the extremely fine distinctions that WordNet makes.

I didn't describe it on the "URI Hierarchy" page yet, sorry about that. It's described in the changelog for now: https://github.com/commonsense/conceptnet5/wiki/Changelog

"music" is a tricky example, because WordNet has finely-distinguished senses of it that appear to be in different WordNet topic areas, even though they all seem to relate to the same meaning. Its different senses are listed in topic areas including "communication", "act", and even "music" itself.