multi-measure rest without a number?

[chip]

I would like to be able to create a multi-measure rest and mark it as 
Free Time, no number of measures, preferably putting the text in the 
middle of the staff, not above or below it. I don't see this in the 
manual, and tried to put text above/below the staff of a regular 
multi-measure rest but it results in an error about lyric mode. I tried 
this -
\property Score.skipBars = ##t R1*2/markup { Free Time }
(also with a space before the /).
Anyway to do either the of the above (text inside the non-numbered 
multi-measure rest or attaching text to the multi-measure rest)?
--
Chip