Scaled durations in scheme

[Fr. Samuel Springuel]

Within a scheme music function, how can I tie the value of the third argument 
of ly:make-duration to the value of the first argument so that the note takes 
up the space of a 1/4 note?  I’m trying to set things up so that I only have to 
change one thing to change the appearance of the note without changing the 
spacing.  For instance, the MWE below uses half-notes.  If I wanted to change 
to whole notes, I currently have to change both the first and third argument.  
I’d like to set things up so that only one thing has to be changed for easier 
maintenance.  The way I figure I need to define a scheme variable and use that 
in some sort of transformation, but converting from an integer for the first 
argument to the fraction expected for the third (or vice versa) has me baffled.

\version "2.19.84"

recite-note = #(define-music-function (note) (ly:music?)
            (withMusicProperty 'duration (ly:make-duration 1 0 1/2) note))

\new Staff {
    \new Voice { g' \recite-note g' g' }
}



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Fr. Samuel, OSB
(R. Padraic Springuel)
St. Anselm’s Abbey
4501 South Dakota Ave, NE
Washington, DC, 20017
202-269-2300
(c) 202-853-7036

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