The degree-type-value type indicates whether the current degree element is an addition, alteration, or subtraction to the kind of the current chord in the harmony element.
<xs:simpleType name="degree-type-value"><xs:annotation><xs:documentation>The degree-type-value type indicates whether the current degree element is an addition, alteration, or subtraction to the kind of the current chord in the harmony element.</xs:documentation></xs:annotation><xs:restriction base="xs:string"><xs:enumeration value="add"/><xs:enumeration value="alter"/><xs:enumeration value="subtract"/></xs:restriction></xs:simpleType>