How to get VLC to play mid/midi files using an SF2 soundfont in Ubuntu Linux 13.04

First, install the fluidsynth plugin for vlc:
sudo apt-get install vlc-plugin-fluidsynth

Close any vlc windows you have open, then open vlc again.
Tools > Preferences
(or just ctrl+p)

In the preferences window choose "All" for "Show Settings" at the bottom left.

Then navigate in the list on the left to:
Input / Codecs > Audio codecs > Fluidsynth

Then click the Browse button for "Sound fonts" and choose your soundfont file.

Save then restart vlc and play a midi file.