References to the physical features (e.g. chains of holes) on the roll copies
that carry this symbol. Since the association might be debatable,
it can be annotated. There might be e.g. doubts about the meaning
and correct transcription of a feature on a physical roll.
This points to a feature by its @id.
ReadonlyidA unique identifier for this object.
A symbol is an abstract musical or textual entity carried by one or more physical features on the roll. Symbols are the result of interpreting the physical features (chains of holes, writings, etc.) on the roll copies.
See
crm:E90 Symbolic Object