Lyric hyphens, preferred and otherwise

[Joel C. Salomon]

Is there a way to indicate that a hyphen is desired here, or that it
is preferred that it be shrunk to nothing?  Consider this example:

\version "2.16.2"
\score {
  <<
    \relative c'' { c2 c }
    \addlyrics { two -- part }
  >>
}

It would be OK with me if this was displayed "two-part" or "two -
part", but I want to avoid having this hyphen disappear: "twopart" is
*not* good.

I've tried `\addlyrics { two-part _ }` and `\addlyrics { "two -" part
}`. They both sort-of work, but is there a more flexible solution?

--Joel