This was an interesting point brought up by a music professor; by the second third of Star Wars, John Williams has introduced and reinforced a number of musical themes: the "Force theme", Luke's theme, and an Imperial theme. However, at the moment of Kenobi's death (certainly one of the most important moments in that film), when all three of those themes would have been more appropriate (and probably in that order), Williams instead chooses to play a stylized version of Princess Leia's theme.
This is an odd choice; Kenobi and Leia have never even properly met, and she seems downright uninterested in what is happening to him right then. Of course there is an in-universe connection between them, but the audience (and possibly most of the cast) would remain unaware of it for the better part of a decade.
My music professor's pet theory is that Kenobi has taken on a paternal role for Luke and so Williams is co-opting Leia's "feminine" familial theme for the entire Skywalker family, thereby foreshadowing that entire connection. This of course requires that he knew the larger arc of the plot during production of the very first film, which I find doubtful, and I think I've even heard it contradicted somewhere before.
The question is, does anybody have any insight into this odd musical choice? Can anybody explicitly confirm or debunk whether Williams knew enough about the plot at this point in time to have been making such a foreshadowing at all?