Autochange staffs with a single voice

[Jérémie Lumbroso]

Hello,

As far as I can tell, the automatic staff changing feature only works by
assigning a voice to a given staff ("up" or "down"). Say now that in your
voice you have chords, some notes of which should be on the upper staff
and others on the lower. It seems as though it's not currently possible
but I may be wrong.

Perhaps there is a way to tell Lilypond to pretend chords <c d> should be
considered as several voices? I know of the voicify shortcut, << c //
d >>, but for some reason that doesn't seem to work (not to mention it is
very tedious).

(Of course, ideally, I should input the music correctly, but as is I can
only export it in single-voice clumps.)

Eventually, I then want to "tighten" the two staves so that the space
between middle C and the D of the upper staff and the B of the lower staff
is the same as the space between two consecutive notes anywhere else on
the staves, see here for an example:

http://img245.imageshack.us/img245/54/staves.png

Does anybody have clue? :-)

Jérémie


PS: I just was in Utrecht, city of our founders!!