+followed by a music expression. If @emph{and only if} the symbols
+are valid LilyPond identifiers (alphabetic characters only, no
+numbers, underscores, or dashes) which cannot be confused with notes,
+the @code{#'} may be omitted and, as a shorthand, a list of symbols
+can use the dot separator: i.e. @code{\tag #'(violinI violinII)} can
+be written @code{\tag violinI.violinII}. The same applies to
+@code{\keepWithTag} and @code{\removeWithTag}.