share note stem between voice

[Daniel Cheng]

Hi list,

I want to digitalize a music sheet I have here.

It have some special feature, and I want to replicate it.

See http://img235.imageshack.us/my.php?image=stemnr2.png

Red note-heads are voice 1, Blue note-head are voice 2.

As you can see:
  - both voice share the same stem
  - the stem directory always towards voice 2
  - when two voice are on the same note, two stem are drew

I know I can use the \stemUp / \stemDown to do this manually,
but I want to know if there are any easier ways.

thanks