Changing the tempo in midi?

[Ben Engbers]

Hi,

As a novice user of lilypond, I am beginning to understand how to enter 
music so that is not the problem.
For playing the score on my Fedora laptop I use Qsynth. I know if it's 
because of that but no matter what I try, the midi file is played in a 
BPM of about 72.

This is the “global” part:
global = {
  \key e minor
  \numericTimeSignature
  \time 12/8
  \Tempo “Presto” 4 = 140
  \dynamicUp

And this is the “score” part:
\{
  <<
    \melodyPart
    \leadSheetPart
  >>
  \layout { }
  \}
    \temp 4=140
  }

What do I need to do to play the midi at a different tempo (BPM=90)?

Ben