I had a friend who asked me yesterday if musicals followed the same conventions as they used to.
First, a brief history:
Musicals are a genre which means there are certain stylistic conventions that have been cemented over time. In contrast, political films are not a film genre. There might be a number of films that have appeared over history about politics, but they have nothing in common with each other. Part of the reason that musicals are a genre with consistent patterns is because the vast majority of the successful musicals since the dawn of the sound era were all produced under one roof: MGM Studios. From the late '30s to the '50s, the genre's top directors-- Charles Arthur, Stanley Donen, Gene Kelly, and Vincente Minnelli-- all worked under a branch of production at MGM under producer Arthur Freed and they likely had the same loose guidelines to follow. Additionally, many musicals that made their mark in the movies (i.e. Brigadoon, Kismet, West Side Story, My Fair Lady, Funny Girl, Hello Dolly, Oklahoma, The Music Man) made their way from Broadway so those Broadway conventions filtered in to most adaptations. Even when conventions weren't borrowed, the directors faced the same challenges in bringing a Broadway production to the silver screen and deciding which versions to keep.
One of the primary conventions of a musical film is the idea of integration (remember folks, you'll have a quiz on those bold words) which is when characters would spontaneously erupt in song and dance as if it was as natural to them as speaking. It's a somewhat silly concept and one that sometimes gets parodied.
Audiences would have found it equally absurd if not for the fact that audiences were gradually weaned off earlier versions of the musical in which the characters were singing in situations that made sense. This is called the backstage musical. In MGM's early Broadway Melody series, and the Busby Berkley productions at Warner Brothers, the plot centered around performers on a stage, so that whenever their characters were singing, it would make sense within the confines of the plot.
One could see evidence of the gradual transition in a film like "Meet me in St. Louis" in which some of the musical numbers make sense within the context of the plot (Judy Garland and Margaret O'Brien singing "Under the Bamboo Tree" to entertain house guests) and some don't ("The Boy Next Door" or "The Trolley Song" are completely unnatural). More interestingly, "Meet me in Saint Louis" has numbers which fall into grey area: In the opening of the film, Judy Garland strolls in singing "Meet me in Saint Louis" and she is joined by her older sister on the piano, before their father storms in and tells them to "turn off that racket." This scene could be taking place outside the context of reality, but when we see the dad (a character who sings no musical numbers over the course of the production) interrupting them, we see the scene differently: it's just two girls getting carried away as they are humming a tune.
Now, the question about whether musicals follow the same conventions as they did before:
The question might have less to do about whether directors have a need to follow conventions as whether or not the makers of modern-day musicals face the same challenges of getting audiences on board as filmmakers did back then (which they did).
The fact that Hollywood didn't really make any musicals for most of the '70s, '80s or '90s is pretty good evidence that modern-day audiences were clearly not familiar and eagerly accepting of musicals at the time. West Side Story, for example, is appreciated by a lot of people, but at the same time, the idea of gangsters being proficient in ballet has been parodied on Family Guy, SNL, and pretty much everywhere else. In order to bring back the musical, Hollywood has had to gradually revert from the integrated musical to the backstage musical. High School Musical and Dreamgirls have had backstage plots, and some of the Broadway-to-movie films that have recently come out on this latest wave (e.g. Rent, The Producers) might have been more acceptable as integrated films because they were integrated musicals on Broadway and didn't tamper too much with the source material. It's also telling that neither of those two films got great reviews anyway.
When a musical does fully embrace an integrated formula like Moulan Rouge, in 2001, it does tend to come out as over the top. Although the sheer ambition of the film was enough to get the film an Oscar nomination and there's a certain class of people who hail the film as genius, the critical reaction and reaction from many moviegoers at the time was fairly polarized (short of going back in time and asking people what they thought of the film right as they walked out of the first screening, I know it's hard to prove that, but that's very much the way I remember it) .
Chicago was able to win an Oscar for best picture as a musical and the unofficial headline in Hollywood was "The musical has officially been revived" (Read the first paragraph of Roger Ebert's 2003 Oscar predictions for supporting evidence: http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/20030316/OSCARS/33010302/1023). Perhaps, Chicago is credited with reinventing the musical because it was able to find a way to make a convincing musical that would go over with audiences while preserving the fun of the integrated musical: Setting the musical numbers in the mind of a character.
Recently, because more musicals have been released in the last few years and the average American moviegoer might be more movie-literate, integrated musicals have done a little better. This past year, Across the Universe and Hairspray (another Broadway holdover) were both greeted fairly well. It could be that filmmakers are gradually learning what works and what doesn't from the few musicals to be released before they started directing their projects.