Nesting variables inside music

[Shadok]

Hi, I am new to LilyPond and I wonder how to use
"local" variables inside a music expression.
I searched the list archives but did not find
anything.

Something like:

melody = { 
  c'8 d' e'
  % long here
  x = {<g e' c'' b''>8}  % local assignment
  \x c \x d \x e         % use it
  % long after
}

It is easy to assign x outside (before) melody, but
if melody is long and the need of \x is local, it
would be more understandable to define it only where
needed.

What are the usual practices for that?

Thanks