Mark Evanier has a good post on the musical Camelot, which had its out-of-town tryout here in Toronto and proved, for the first of many times, that the O'Keefe Centre was too damn big.
The big post-opening rewrite of the show that Evanier mentions meant that several songs that were recorded for the cast album were not heard in the show after the first few weeks. Moss Hart dropped the cute but utterly pointless "Then You May Take Me To the Fair," as well as the knights' chorus "Fie On Goodness," a great number that unfortunately held up the show at a crucial moment.
Cast albums in those days were recorded on the first Sunday after the show opened, and released within the first couple of weeks after the show opened; cast albums were huge sellers then, and it was necessary to get them out as quickly as possible to take advantage of a show's success. Because of this, it was quite common for cast albums to preserve arrangements, sections of songs, and even entire songs that were dropped after the opening. Also, because the cast album's liner notes were often prepared before the show had even opened (because of the necessity to get the albums out as quickly as possible), you would sometimes find that the plot synopsis on the album differed from the plot of the actual show.