Explanatory notes
… the system of notation (e.g., tonic sol‑fa, staff notation, numerical symbols, Braille music). The music in this heading … catalogues, etc., containing musical notation which is merely subsidiary or illustrative of the text, e.g., a … headings 49.01 or 49.11 ). (b) Cards, discs and rolls for mechanical instruments ( heading 92.09 ). …