code: Rule InlineField() {
  		return FirstOf(IfieldArea(), IfieldBook(), IfieldComposer(),
  			IfieldDiscography(), IfieldGroup(), IfieldHistory(), IfieldLength(),
  			IfieldMeter(), IfieldNotes(), IfieldOrigin(), IfieldPart(),
  			IfieldTempo(), IfieldRhythm(), IfieldSource(), IfieldTitle(),
  			IfieldVoice(), IfieldWords(), IfieldLyrics(), IfieldTranscription(),
  			IfieldKey(), IfieldUserdefPlay(), IfieldUserdefPrint(),
  			IfieldInstruction(), IUnusedField()
  			).label(InlineField);
  	}
docs: inline-field ::= ifield-area / ifield-book / ifield-composer
  / ifield-discography / ifield-group / ifield-history / ifield-length
  / ifield-meter / ifield-notes / ifield-origin / ifield-part
  / ifield-tempo / ifield-rhythm / ifield-source / ifield-title
  / ifield-voice / ifield-words / ifield-lyrics / ifield-transcription
  / ifield-key