footer strings

[Clément]

Hi, 
I try to write parts for several instruments.
I would like to make the instrument name appear at the bottom of each page.
So I tried to use oddFooterMarkup as it works for all pages. 
( if evenFooterMarkup is not defined. )
I don't have any warning at compilation but it does not work.
I already done this for page number as it is explained in the manual, 
also for part title.
As the part title does not change for every instrument, it is defined in the
global header of the part, this seems understandable.
Following what I tried to make :
  oddFooterMarkup = \markup \fill-line{
    \bold \concat {                        
      \fromproperty #'header:title " - " 
      \fromproperty #'header:instrument " - "
      \fromproperty #'page:page-number-string
      }
    }
I included this in my global paper block, just before a global layout block that
is followed by the book block where I define all scores that I want to be
included. 

Can someone explain me why it doen't work, and possibly teach me a way to do 
this?
I would be gratefull because I already spent a lot of time searching on the
internet and did not found any corresponding information.
I am not very skilled in scheme. I tried to look around in the doscumentation
and on the net this because it seemms to be the easiest way to tweak parameters,
but did not find or understand something appropriate.
Thank you for help.