calculating relative pitch after polyphony measures ...

[Xiaoyu Ding]

In Lilypond document, it says:

Polyphony does not change the relationship of notes within a \relative { } 
block. Each note is calculated relative to the note immediately preceding it. 

\relative { noteA << noteB \\ noteC >> noteD }

noteC is relative to noteB, not noteA; noteD is relative to noteC, not noteB 
or noteA.


But in the following section, the last line's c note seems to be relative to 
the as8 in the first voice instead of relative to as4. in the second voice.

Could you explain why that's the case?

bottom =  \relative c {
 \override TextScript   #'padding = #2
 \key as \major
 \time 2/4
 \clef bass
 
 as4( des |             %1
...
  << {
  c16 es c es c f c f |
  des f des f bes, es bes es |
  r es g es as8 r |
 } \\ {
  c,8 c f,4( |
  bes  es,) |
  as4. r8 |
 } >>
 r16 c c c c c c c |            %17


Thanks.

Xiaoyu