<xs:simpleType name="show-frets"><xs:annotation><xs:documentation>The show-frets type indicates whether to show tablature frets as numbers (0, 1, 2) or letters (a, b, c). The default choice is numbers.</xs:documentation></xs:annotation><xs:restriction base="xs:token"><xs:enumeration value="numbers"/><xs:enumeration value="letters"/></xs:restriction></xs:simpleType>