Multiple parts on the same stems

[Gerardo Ballabio]

Hello all,
I'm trying to typeset a percussion score with several instruments on
the same staff. When they play simultaneous notes I want to line them
up all on the same stem, like this (output attached, percussion1.pdf):

%%%%%%%%%%
\version "2.24.1"

\new Staff \relative {
  \clef "varpercussion"
  \stemDown
  R1 |
  r2 <e b' f'>2\f-> |
  R1 |
  r2 q2-> |
}
%%%%%%%%%%

But I'd like to write down each part separately, so that I may also
print the single parts without redoing everything. And I also want to
use different note heads for each instrument.
This is the best I could come up with:

%%%%%%%%%%
\version "2.24.1"

bassDrum = \relative {
  \stemDown
  s1 |
  s2 b2-> |
  s1 |
  s2 b2-> |
}

cymbals = \relative {
  \override NoteHead.style = #'xcircle \stemDown
  s1 |
  s2 f'2 |
  s1 |
  s2 f2 |
}

tamTam = \relative {
  \override NoteHead.style = #'cross \stemDown
  s1 |
  s2 e2 |
  s1 |
  s2 e2 |
}

pause = \new Voice {
  \clef "varpercussion"
  \time 4/4
  R1 |
  r2 s2\f |
  R1 |
  r2 s2 |
}

percussions = \new Voice \relative {
  <<
    \cymbals
  \\
    \tamTam
  \\
    \bassDrum
  >>
}

\new Staff
<<
  \pause
  \percussions
>>
%%%%%%%%%%

But as you can see (output attached, percussion2.pdf) the three notes
aren't aligned on the same stem, only two of them are.

I tried \partCombine, it works nicely with two parts, but if there's a
way to combine three or more I didn't find it.

Any help is much appreciated.

Thanks
Gerardo

percussions1.pdf
Description: Adobe PDF document

percussions2.pdf
Description: Adobe PDF document