@layer(optional)Identifies the layer to which a feature applies.
@part(optional)Indicates the part in which the current feature should appear. Use 'all' when the
feature
should occur in every part or 'none' when the feature should not appear in any part.
@partstaff(optional)Signifies the part staff on which a notated feature occurs. Use 'all' when the
feature should occur on every staff.
@staff(optional)Signifies the staff on which a notated event occurs or to which a control event
applies. Mandatory when applicable.
@startid(optional)Holds a reference to the first element in a sequence of events to which the feature
applies.
@tstamp(optional)Encodes the onset time in terms of musical time, i.e., beats[.fractional beat part],
as expressed in the written time signature.