This paper presents the alpha version of Tonalities’ annotation interface. This interface leverages web technologies to grasp how distinct theoretical viewpoints bring to light different, sometimes conflicting, musical properties; to confront different analytical interpretations; and, ultimately, to provide reasoned, documented and authored statements on musical pieces. To this end, Tonalities (a) makes use of theoretical models, which (b) can be associated with arbitrary selections on the score and (c) lead to critical analyses through collaborative approaches. Three types of semantic data are used: MEI scores converted to RDF triples, music-theoretical knowledge formalized in the form of OWL ontologies, and semantic annotations expressed as CIDOC-CRM events.