N'th time bar markup

[Richard Shann]

Dear List,
The example given in the docs
http://www.lilypond.org/doc/v2.18/Documentation/notation/long-repeats#index-volta-bracket-with-text
 for n'th time bar with arbitrary text uses a separate definition for
the markup to be placed in the n'th time marker. This is a bit awkward
to output from Denemo, and would not help clarity in any case, as the
definition would only be used once and would be widely separated from
its use.
So, I would like to "inline" the markup, but I'm having trouble figuring
out what scheme is seeing for the defined value. I've put in a
#(display ...) to print out the scheme representation, but I'm not quite
up to deciphering this. So if someone could put me out of my misery and
say what needs to go in place of the ???? in the following to allow me
to uncomment those lines and drop the definition at the head, I would be
grateful.

\version "2.18.0"
voltaAdLib = \markup { 1. 2. 3... \text \italic { ad lib. } }
#(display voltaAdLib)

\relative c'' {
  c1
 % \set Score.repeatCommands =
 %   #(let ((voltaAdLib ?????)) (list(list 'volta voltaAdLib) 'start-repeat))
  c4 b d e
  \set Score.repeatCommands = #'((volta #f) (volta "4.") end-repeat)
  f1
  \set Score.repeatCommands = #'((volta #f))
}


Richard