tied same-note chords

[Carla van De Sande]

I want to have a tie across
two chords, each of which consist
of the same two notes.  I have
used \slurUP and () but can't
figure out how to combine this
with having the same note with
stem up and down.

An example of this is measure 4 of
http://www.geneva.edu/~bvds/music/cat27.pdf.

So, I want the side-by-side notes printed
as a single note, with two stems (up and down).
AND I want this tied.

Thanks.
Carla van de Sande

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