code: Rule TimeSignature() {
  		return FirstOf(
  				String("C|"),
  				String("C"),
  				IgnoreCase("none"),
  				MeterNum(),
  				DIGIT()
  		).label(TimeSignature);
  	}
docs: time-signature ::= %x43 / %x43.7C / "none" / meter-num / 1*DIGIT<p>
  <tt>C</tt>, <tt>C|<tt>, <tt>none</tt> or numeric