degree-type-value

<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>