I think the St George's books theme was used that way afterwards (i.e. GK2 & 3) but originally the main theme was the "Gabriel's theme" as per
this website.
Having said that the St George's books theme is really a variation on the main theme anyway so take your pick!
EDIT: Please feel free to correct this anyone if i'm mistaken!
In relation to the clock...
Spoiler:I think the reason you could move it was so you could rummage through the chest, although from memory there wasn't anything of interest in there anyway?
I thought that you couldn't play with the clock if it was on the chest although I may well be wrong...