Adding an extra staff

[alistair zaldua]

Dear Lilypond community,
Please excuse my question, I am new to Lilypond. I work on a Mac 10.3.9  and operate with version "2.11.56-1".
I've been looking at the page concerning "adding extra staves" and although I find the  example clear, but it's also insufficient because as soon as I want to write quicker note values within the middle stave, they tend not to get engraved in the bar with "3-staves".

Since I'm currently typing up a piano score I wanted to test out the trick in a PianoStaff. So, my code looks like this:


\version "2.11.56-1"
\score {
        <<
        \new PianoStaff <<
            \relative c''
            \new Staff {
            \time 4/4 g8 a b c d c b a     %scale 1
            gis ais c des es des c bes     %scale 2
            a b cis d e d cis b         %scale 3
            c d e f g f e d             %scale 4
            es f g aes bes aes g f         %scale 5
                        }   
            \new StaffGroup \relative c'' {
                \new Staff { r1 gis4 gis gis gis
               
            << a1 \new Staff { \once \override Staff.TimeSignature #'stencil = ##f a8 g a g a g a g }  >>
            c4 c c c     }
                    }
                >>
            >>
        }

This works, and I am happy !
However whenever I type in more notes into the  middle bar, it bunches all those notes into the first quarter  i.e.:

  << aes8 ges aes ges aes ges aes ges \new Staff { \once \override Staff.TimeSignature #'stencil = ##f a8 g a g a g a g }  >>
 
these didn't work either:
<< aes8 \new Staff { \once \override Staff.TimeSignature #'stencil = ##f a8 g a g a g a g }  ges8 aes ges aes ges aes ges >>

<< aes \new Staff { \once \override Staff.TimeSignature #'stencil = ##f a8 g a g a g a g }  >> ges8 aes ges aes ges aes ges


I tried this out in the previous version I was using , which was "2.10.33" and that didn't work. Where should I type the notes for the middle bar ?

Many thanks in advance for any help.