passing a Context to a scheme function (format-metronome-markup)

[Graham Percival]

I'm experimenting with calling (format-metronome-markup) directly,
but I'm having difficulty with the context argument.
   // main code:
(define-public (format-metronome-markup text dur count context)
...

My code:
\header{ 
  piece = #(format-metronome-markup "Allegro" 4 120 'Global)
}
\relative c' { c }

Error message:
foo.ly:3:11: error: GUILE signaled an error for the expression
beginning here
  piece = #
           (format-metronome-markup "Allegro" 4 120 'Global)
Wrong type argument in position 1 (expecting Context): Global


I've tried #f, '(), 'void, 'Score, and a few other things I can't
remember.  The only time that context occurs in the function is
  (let* ((hide_note (eq? #t (ly:context-property context
'tempoHideNote))) which doesn't concern me -- I want this to always
resolve to false.  How do I give the function a Context?

Cheers,
- Graham