How to get "N.C." in a chord line

[Holly Briscoe]

Hi again to the absolutely terrific list!

In my current score, there is a measure without a chord, so I put s1 in the 
\chordmode section. Nothing prints above the chordless measure, but since I 
also have \set chordChanges = ##t, the performer will think the chord from the 
preceding measure ought to be repeated. The score I'm working from has "N.C." 
above the measure.

I can find no example in the manual, the tips and tricks, the examples, or the 
regression tests of how to get "N.C." printed wherever there is a chord rest. 
Did I just miss it?

Thanks,
Holly