staff

<xs:group name="staff">
  <xs:annotation>
    <xs:documentation>The staff element is defined within a group due to its use by both notes and direction elements.</xs:documentation>
  </xs:annotation>
  <xs:sequence>
    <xs:element name="staff" type="xs:positiveInteger">
      <xs:annotation>
        <xs:documentation>Staff assignment is only needed for music notated on multiple staves. Used by both notes and directions. Staff values are numbers, with 1 referring to the top-most staff in a part.</xs:documentation>
      </xs:annotation>
    </xs:element>
  </xs:sequence>
</xs:group>