where does the melisma-LyricText #X-offset setting live?

[Kieren MacMillan]

[ Lilypond 2.9.11 ]

Hello, all!

I would like to modify the way Lilypond left-aligns melisma Lyrics: I  
feel it's *too* (i.e., exactly) left-aligned, so I currently use

    lyrMX = \once \override LyricText #'X-offset = #-0.5

before each melisma syllable to compensate. I'd like to make this a  
global adjustment (in my init_Score stylesheet), but don't know how/ 
where to do such a tweak (since it won't be for *all* LyricText, but  
just a melisma syllable).

Any help would be appreciated.

Thanks,
Kieren.