How can I make chord symbols part of \markup or similar?

[James Lowe]

Hello,

I have read the notation manual and the LSR and have experimented 
unsuccessfully in trying to explicitly set the Chord Symbols as a 'markup' to a 
given note.

For example

--

myvariable = { \chords {c4:m} }

\score { a b^\myvariable  c d }

--

The idea is to get the nice C minor (Cm) symbol above the b.

However I get

42:37: error: syntax error, unexpected MUSIC_IDENTIFIER

What I didn't want to have to do was have to set an entirely new 'voice/score' 
with the few chords explicitly set amongst  a slew or spacers or R1s if that 
make sense.

Is there a way I can do this without resorting to simply   b^"Cm"   which does 
the same thing, but not as nicely as the chord font.

James