to MIDI or not to MIDI

[Maury Merkin]

I'm brand new to Lilypond having just heard of it yesterday
for the first time ever.  I have several hundred questions
but we'll take 'em one at a time.

I've got a file foo.ly which compiles with no error messages
and 'ly2dvi -P foo.ly' produces the desired foo.ps just as I
desire but I can't figure out how to produce a midi file.

Here are the last several lines of foo.ly:
-------- begin --------

\score {
 \simultaneous {

  %\accompaniment
   \context ChordNames
    \accompaniment

  \melody
  }
 }
 \midi  { \tempo  4 = 72  }
 \paper { linewidth = 10.0\cm }

--------  end  --------

TIA for any pointers.

Maury