three voices and rest

[Federico Bruni]

Hi,

I'm writing a three voice music.
voiceOne is the melody, voiceTwo is the bass and voiceFour is the
accompaniment.
I've followed the Voice order suggested in NR 1.5.2 and I've chosen
voiceFour for accompaniment because I want the stems to point down, like
bass notes.

The problem is that the rest of voiceFour is printed under the second
voice and not between first and second, as I would like it to be.
Is it a normal behaviour?
I'm doing something wrong?

Thanks for help!
Federico

############################################################

\version "2.13.38"

first = \relative c' {
  e2.
  
}

second = \relative c {
  a2.
  
  
}


fourth = \relative c' {
  r4 <a c>  q
}

\new Staff <<
  \time 3/4
  \clef "G_8"
  \new Voice { \voiceOne  \first }
  \new Voice { \voiceTwo  \second }
  \new Voice { \voiceFour \fourth }
>>