Notes with different pitches sharing a staff line are engraved strangely

[Dan Eble]

> I'm not top posting.
% This example might be worth more than one ticket.
\version "2.18.0"
\language "english"

upper = \relative { bs'4 }
lower = \relative { b'4 }
chord = \relative { <bs' b>4 }

% In this case, the output clearly represents something other than the
% input.  The input doesn't make much sense in the kinds of music I'm
% familiar with, so I don't think there is a major problem with what
% Lilypond has done except that it should warn that it did not engrave
% what was requested.
\score {
  \new Staff <<
    \set Staff.instrumentName = "<< \\\\ >>"
    \dynamicUp \upper
    \\
    \dynamicDown \lower
  >>
}

% In this case, I'm not sure what the output represents, but unless
% Lilypond is already engraving the expected musical notation, it
% should warn.
\score {
  \new Staff <<
    \set Staff.instrumentName = "< >"
    \chord
  >>
}

% The part combiner can choose either to put the two notes in separate
% voices or in the same voice.  Is the current behavior the better
% choice in this case?  Possibly not.
\score {
  \new Staff <<
    \set Staff.instrumentName = "partcombine"
    \partcombine \upper \lower
  >>
}

% ... and the CAPTCHA is "oddities."  How appropriate.  :-)