Lyrics of a Voice above the Staff of the Voice

[Robert Waniek]

Hello together, 
I'm working on a sheet where the lyrics of the Soprano are set above its staff
because the staff is shared with the Alto which has lyrics differing from those
of the Soprano at some positions (which I read by using \skip).
As far as I have 4 stanzas, using markups is not a usable workaround.
Recently I got to:
\override LyricText #'extra-offset = #'(0 . 20)
But this leaves the hyphens below the Staff and only moves the text into other
page items.

So the question is:

How do I get the lyrics above the staff of the voice they are assigned to by
\lyricsto?

Thanks in advance for any help.

Greetings
Robert Waniek