Hi all.  Julien suggested I post this, and is hosting it for me as I only have short-term storage at present.  This was a birthday present for him.
 

http://juliencoder.de/q/BirthdayFugue.mp3

 

I did the original MIDI file in Windows, but from there all was done in Linux.  MIDISH to play the MIDI file, and Nama/Ecasound for recording.  The organ is a

jOrgan disposition for an American Classic organ, perhaps something in the style of the 1930's/40s.  jOrgan is playing SF2 soundfonts through Fluidsynth.  Enjoy.

 

Kevin