code: Rule AbcMusic() {
  		return ZeroOrMore(
  			SequenceS(
  				ZeroOrMore(WSP()).suppressNode(),
  				FirstOfS(
  						Xcommand(), Comment(), 
  						TuneField(), AbcLine(),
  						Tex()
  				)
  			)
  		).label(AbcMusic);
  	}
docs: abc-music ::= *(abc-line / comment / xcommand / tune-field / tex)