A couple of pieces on musical theatre that are worth looking at:
This article (called to our attention by Mark Evanier, talks about the decline of the original cast album. I think eventually producers of musicals will have to stop thinking of cast albums as a way to finance their shows and start thinking of them as part of the budget -- that is, pay to have the album recorded, to help publicize the show to people outside New York. The days when record companies would get into bidding wars over cast-album rights are over, and the end of that era is very clearly marked. In 1964, the cast album of Fiddler On the Roof went gold for RCA (which had invested in the show to get the cast-album rights, a common practice). In 1966, a hit from many of the same people, Cabaret, produced a cast album that sold well but didn't achieve bestseller status, and the producer of the show, Hal Prince, called the record company and demanded to know why it wasn't selling as well as Fiddler. It was because Broadway had changed, popular music had changed, the record industry had changed. Except the record industry never really adapted to these changes, and neither did Broadway. One thing that I suspect we may see more of in the future: in 1971, a flop show, The Grass Harp, got a cast album by having the orchestral tracks recorded in Europe (where session fees are much lower) and then having the performers overdub the vocals in America. I would not be at all surprised, given how much it costs to record in America, to see a few more cast recordings with the London Symphony Orchestra subbing for the original pit band.
Also, Mark Steyn, deranged as a political columnist but improving as a writer on theatre (maybe some derangement is necessary for that job?) has some pieces on musicals from a few years ago, here, including an interview with Lionel Bart that also appeared in his very uneven book Broadway Babies Say Goodnight, and a good account of the significance of Oklahoma! (Incidentally, I erred in saying that Bob Merrill was the sloppiest rhymer ever to have a successful career as a theatre lyricist. Lionel Bart, whose last performed lyric rhymed "gluttony" with "utterly," was much sloppier.)