Willy Wonka and the Chocolate Factory - Wrong Tune
When Willy plays a short tune on the "musical lock" to the door to the chocolate room, Mrs. Teevee identifies it smugly as "Rachmaninoff." It's clearly from a Mozart piece. Perhaps intended to indicate Mrs. Teevee is full of hot air, but not likely--only classical music fans would get it.
I noticed the misidentified tune as well. I have always that it was included like you said to show that Mrs. TeeVee is not as smart as she thinks she is. I really doubt that they would leave that obvious (even if only to a select audience) error in the movie. Look at it this way, Disney always inserts jokes and sayings that only adults (not talking about the "dirty" things) would understand. Perhaps this joke was intended to appeal to a more "cultured" audience.
Okay, umm, yeah that's supposed to be there.
The point of that part WAS to show that Mrs. Teevee is full o'crap. In the movie you see how she raises her kid, and she thinks there is nothing wrong with it, but obviously there is. Also, remember when Mr. Wonka is telling the group where the oompa loompas come from, and she tells Wonka that she is a "teacher of geography" and she KNOWS that there is no such place. But OF COURSE there is, because how else could Wonka have found them? And Wonka is right, because he always is and he is a genius. So there is another place where the audience can see that this woman is stupid and is raising her kid wrong and needs to get a life.
In conclusion, whoever submitted this is terribly wrong by claiming this as a slip up.
This was a JOKE. It was supposed to be funny. Obviously, not every audience member would get it, but those who did could laugh and feel a little smug. Take a look at Mr. Salt's face immediately following the comment if you aren't sure.
If you need convincing that this is not a slipup watch that part of the movie with the directors commentary turned on - he comes right out and says mis-naming the composer was supposed to be a joke but it feel flat because in screenings nobody got it.
I have a commementary book on Making Willy Wonka, and it in it Mel Stuart says that he thought the joke was pretty funny, but now thinks he should of used a more common tune. (A lot of people didn't get it.)
I saw the movie back in 1971 when it was released. Mrs. Teavee's mistake was obviously intentional, because Wonka corrected, or rather mis-corrected, it by replying "Chopin, I should think," in response to Mrs. Teavee's "Rachminoff". Wonka's reply has been edited out of every version of the movie I have seen since then, and, since Mozart's work is now more widely known since the release of "Amadeus", I sincerely doubt that it will get put back in.