GeoCOCO VS tree-labeller

I come from a similar application area, where I try to tag (annotation/label) a taxonomy of products iteratively. You are trying something slightly different, AFAIU, labeling a flat set of songs, each song with a set of tags from ontology (directed graph)From an application point of view, this is what taxonomists often do, when migrating products from one catalog to another: mapping one taxonomy to another. There was quite active research on matching ontologies. So, there are tools in both industry and research that help in that process, although I have never researched whether they do it iteratively and using sampling. Another related area is labeling data to train machine learning models (in your case it sounds a bit like multilabel classification, in my case, this is multiclass classification). This is often done iteratively, and tools like Explosion Prodigy samples for manual annotation only those items that the ML model is still not confident enough. This might be offtopic, but I looked at your library and your notation for defining relations between tags, reminded me of RDF and OWL languages for defining ontologies. They are quite well-defined and have tools for making inferences (reasoners).