Rita Moreno can definitely sing, and she has a great voice! She's sung on variety specials, the Electric Company, etc. And she sings "America" in the movie WSS, and the beginning of the Quintet just as mentioned before.
Back in that "golden age," they used to care about getting the right voice quality for a specific song or character. Some ladies had gorgeous soprano voices, but if they were playing a role that called for something more smoldering and low, they would be dubbed by someone with the appropriate tone.
Today, they barely care if anyone can hold pitch. And if they can, they're called "good singers."
Of course most of the material being done in musicals today doesn't called for highly trained vocalists the way a Rodgers & Hammerstein ballad does, or something by Bernstein or Sondheim. The pop sounds today require little training at all. Belt loud and on key, riff a little ... and if you're a star, you're hired!
Also there is a huge stigma placed on dubbing in films now, which I think is completely ridiculous. This isn't the same as Milli Vanilli who were passing themselves off as singers in the music business. And it's not the same as paying to see a live concert of a singer and getting a playback track instead.
These are movies. Nothing is live. Nothing is real. It's all prerecorded, processed, rerecorded, retaken, and enhanced with both visual and audio effects.
So, why not dub? Just convince me that it's "really you" singing. If you do it badly, I'll complain, just like if a star jumps out a window in a movie and suddenly gains 20 pounds for the one shot, I'm gonna call "foul!" That's a bad stunt double.
But I agree with Stanley Donen, who disagreed with Jean Renior's comment: "Film is truth for 24 frames per second." Donen countered with, "Film is actually a lie for 24 frames per second."
Just don't get caught doing it.
"Jaws is the Citizen Kane of movies."
blocked: logan2, Diamonds3, Hamilton22