I'm just starting to read libretti to musicals that I haven't done or that I can't watch, and I started with--of all things--All American. After finishing it, because I have such an insatiable appetite to know all things about musicals, I read some synopsis elsewhere online, and those sources touched on some scenes and even characters that I didn't read in the script. Specifically, it mentioned that the character Susan was in trouble for sneaking into the men's dormitory and that the character Bricker was caught by a teacher sneaking out of Susan's dorm.
I don't either of these scenes. Granted, this is an old one, and it may be difficult-to-impossible to find an original copy or scan of the script from its original Broadway production, so I'm not looking for confirmation that these scenes did or did not happen in the original run. Rather, I'm wondering if anyone knows whether broadway libretti and scores and paired down when a retail or performance copy of the show gets released. If so, does anyone know why? My assumption is that these changes might be post-show edits for pacing, show length, or whatever. I also wonder if some of the songs are removed, shortened, or lowered to make the material accessible for student and community productions.
I did a little bit of internet sleuthing, and it appears that All American had a bit of a turbulent development process. It's book is credited to Mel Brooks, of all people, who never finished the second act (it was 1962, so he was presumably busy with The 2000 Year Old Man and Get Smart), and it was handed off to Joshua Logan, who also directed the Broadway production. Logan had a wildly different writing style than Brooks, and he was also starting to suffer from bipolar disorder, so the book was kind of a mess and the show flopped. The version licensed by Dramatic Publishing Company (the version I'm assuming you read, adds another writing credit, June Walker Rogers, a Broadway dancer-turned-writer (who coincidentally passed away back in July). Presumably, she did a rewrite of the original script to meld the original two visions, and make it more suitable for licensing and production, which is what you read.
To answer your broader question of when/why published scripts to musicals are different than their Broadway versions, it happens often, for several reasons. Many shows have significant rewrites between Broadway and the National Tour (modern examples of this include Shrek, Mean Girls, and The Addams Family), either to better suit a production that's on the road, or possibly because the writers wanted to take another stab at the material. There are also "high school" versions of shows, that may cut technically challenging songs, rewrite scenes to be age-appropriate, or transpose keys to suit younger voices. (MTI has a huge library of high school, TYA, and Jr. titles). Finally, older, outdated shows may be rewritten, either by the original writers or by new ones (as in the case of All American) to better suit modern sensibilities. This may be to change aspects that are now seen as politically incorrect, or they may be to flesh out the plot to meet modern audience expectations (books for musicals used to just be excuses for songs to occur, there wasn't much thought put into dramatic structure).
Nevertheless, it's an interesting and exciting world, and looking at the scripts for musicals that you can't experience through watching or doing is something I wished more people did. There's a world of phenomenal shows that don't get performed anymore for any number of reasons, and fade into the ether if it weren't for the published scripts being discovered again.
In Martin Short’s biography, he talks about the work he and one of his collaborators did on the revised book for Little Me. It was intended to be the licensing version, but that never really came to be and the new orchestrations were lost in a flood.
This is common. As others have said the published libretto often has been revised since the original performance version (an example that comes to mind is that Hirson and Schwartz legally won the rights to have their revisions to Pippin, and not the Fosse production, published when it initially was.) Of course with some shows there are examples where different editions reflect different versions--the 1971 Follies and to a lesser degree the 1970 Company have different books than their currently licensed versions and the most recently published versions of both reflect those differences, though you can still easily find the *earlier* published versions.
This, of course, is reflected in plays too. Angels in America has at least two published editions which show all the more recent revisions Kushner has made (mostly to Perestroika.) I learned the hard way to be careful when teaching Tennessee Williams' Cat on a Hot Tin Roof. The most commonly published version reflects the original published version which offers the Elia Kazan Broadway Act III as well as the version Tennessee Williams wanted. But then if you try to watch a complete version of the play you will invariably find the 1974 revision made for Broadway by Williams which has many significant differences.