Paul,
It might be worth you trying the following.....
Right-click on the MA3 desktop icon, (or the
Marine Aquarium 3 program in the Start list), then click on 'Configure' and then 'Music Playlist'
You will hopefully then have a version of CanonGuitar.sgt back in the list.
If not, - here is a MP3 version...
www.cjmaddy.co.uk/forum/CanonGuitar.mp3 - (This is a large file, so I will not leave up for a long period)