Setting default text font

[Chris Jones]

I am unsuccessfully trying to globally change the default text font that
is lilypond uses in its pdf output (title of the song, lyrics, etc.

I tried adding this statement at the top of my .ly input file
immediately after the version statement:

|  \version "2.18.2"
|
|  \paper {
|    top-margin = 12
|    #(define fonts
|      (set-global-fonts
|       #:roman "TeXGyreSchola"
|       #:sans  "TeXGyreHeros"
|       #:typewriter "Terminus"
|      ))
|  }

or this:

|
|  \paper  {
|    #(define fonts
|      (make-pango-font-tree "TeXGyreSchola"
|                            "TeXGyreHeros"
|                            "Terminus"
|  }

Whichever font(s) I specify I am still getting the same font. At
a glance, it looks like Microsoft's "Times New Roman", which is not
suited to my purpose.

This being on a linux system (debian stable) I have checked via
"fc-match TeXGyreSchola" commands (etc.) that the font(s) I specified
is(are) correctly recognized by fontconfig and that they are not
substituted.

Could this mean that the above only "defines" the fonts to the system
but that I also need to explicitly invoke them (so to speak) where
needed? Via "\override" commands, possibly...?

I am at a loss to understand how/where lilypond's default configuration
(including fonts) is defined on a linux system. I would have expected to
find some form of lilypond configuration file(s) in the /etc directory
but I have not found any. 

Thanks,

CJ