code: Rule LongGracing() {
  		return FirstOf(GracingGrace(), GracingStyle(), GracingLen(),
  				GracingFinger(), GracingPhrase(), GracingExec(),
  				//!fermata! before !f!
  				GracingVol(), GracingOther())
  			.label(LongGracing);
  	}
docs: long-gracing ::= gracing-grace / gracing-vol / gracing-style / gracing-len
  / gracing-finger / gracing-phrase / gracing-exec / gracing-other