"Singin' in the Rain" is a film about innovation. The possibility to synchronize sound with images in the 1920's was a major overhaul for Hollywood film industry.
During the film.
We can see how people react to innovation when a "talkie" is presented during a private event. A quote excerpted from that time: "Who the hell wants to hear actors talk?" Harry M. Warner, Warner Bros Pictures, 1927
Don Lockwood is able to adapt to this new environment while Lina Lamont, who is good looking but features an awful high pitched voice, cannot do it.
OK, Innovation is here, but the 1st version of the talkie is awful. Then the participants find a way to really take advantage of this new technology by recording sound and film separately and then post synchronizing both afterwards. "Genius is one percent inspiration, and ninety-nine percent perspiration." Thomas Edison
There are also several brainstorming sessions. "To have a great idea, have a lot of them." Thomas Edison
Then a final battle occurs between the "voice" and the "image" that do not come from the same person anymore. Innovation triggers new challenges.
By the way, it's really a great film...