Am 08.09.2016 um 07:14 schrieb Noeck:
Hi David,
it is on the same page in the docs:
http://lilypond.org/doc/v2.18/Documentation/notation/multiple-voices
The normal \voiceOne and \voiceTwo contruct shows each voice with their
stems (and slurs etc.) in different directions.
Partcombine is exactly for the case you don't want: to print two voices
combined into one without different stems for same notes.
Cheers,
Joram
But on the very same page are also described the commands
\partcombineApart
and
\partcombineApartOnce
which do exactly what you need (if I'm not mistaken completely).
Urs