optional Dynamics with tag#?

[Johannes Roeßler]

Dear Lilypondians ;)

another day another question - I try to make optional dynamics for a critical edition,
is it possible, that just dynmaics signs can't be toggled with tags?

----8<--------

\version "2.19.58"

music = \relative {
  g'8. c32 d \tag #'dyn {\p } c32 d
 }
\score {
  \keepWithTag #'dyn \music
}

--->8----------------

Do I really have to use

\tag #'dyn {a4\p} \tag#'nodyn {a4}

and than either \keepWithTag #'dyn \music or \keepWithTag #'nodyn \music?

Cheers Joei