The Audio Features Ontology allows for the description of signal processing results on the Semantic Web. This ontology expresses some common concepts to represent features of audio signals. It mainly relies on the Event ontology, in order to classify particular parts of the timeline backing an audio signal. It also supports dense features, such as chromagrams, onset detection function etc.
The following map shows how a few sample Audio Features Ontology classes (in white) fit in with related ontologies, including the Music Ontology. See the Sonic Annotator page for a different overview.