PianoStaff.shortinstrumentName

[Robert Blackstone]

Dear List,

How can I give a piano staff not only a full instrument name for the first 
system but also a short name for the subsequent systems.
Now I have: 

\new PianoStaff        <<
         \set PianoStaff.instrumentName = "Basso Continuo"
         \set PianoStaff.shortinstrumentName = "B. C." 

but only the first system gets its name

I admit that " \set PianoStaff.shortinstrumentName = "" "  was only a guess 
since I had not been able to find the correct command anywhere in the 
documentation.

Thanks in advance for any help.

Best regards,
Robert Blackstone