combining stems

[Simon Dahlbacka]

I'm (a relative newbie) trying to typeset a choir-type piece, where I'd have SAT on one staff, *with* combined stems,

Now, I realize that I can do it by adding everything as chords, but this does not feel natural to me, and I'd like to keep the different voices separate in the input file if at all possible,

I tried to set them as different voices, and overriden stem direction to be \stemUp, which is not ideal but better than S-up A-down T-up. This works, sort of, as long as the duration is quarternotes or longer (and ignoring the fact that I get a sh*tload of warnings), the beams do not combine, rendering things seen in attached screenshot, 
(from

sopranThree = \relative c' {
  d8 e16 f ~ f8 g16 e ~ e8 d16 c r8 c16 d ~ |
  d8 e16 f ~ f8 g16 a ~ a4 ~ a8 d16 d16 ~ |
  \key g \major
  d1 |
}

altThree = \relative c' {
  b8 c16 d ~ d8 d16 c\( ~ c8 a16 g\) r8 g16 b ~ |
  b8 c16 d ~ d8 d16 g ~ g4 g8 h16 h ~ |
  \key g \major
  a1 |
}

tenorThree = \relative c' {
  s1 | s4 s8 s16 d16 ~ d4 ~ d8 g16 g( |
  \key g \major
  fiss1 |
}
)

So, how am I supposed to merge stems and beams (into chords, but without writing them as chords)?

regards,

Simon


I'm using 2.8.0 on windows FWIW.



A somewhat related note, the documented behaviour about stem directions when using \partcombine seem to be off, or there's a bug in section

8.3.1 Automatic part combining

 http://lilypond.org/doc/v2.8/Documentation/user/lily-781809215.png

non-combining-stems.png
Description: PNG image