Ok, i have heard this song several places, so i am to assume it is a classical piece of some kind. The only place i can think of off hand specifically though is in the movie “Who Framed Roger Rabbit?”. When Eddie Valliant goes to the Ink and Paint club, Donald and Daffy duck are both playing this song (kind of dueling style) on pianos whilst attacking one another in a cartoonish fashion. Is that vague enough for you? Thanks in advance… 
-Dani
No idea, but IMDB lists the soundtrack as:
“Why Don’t You Do Right?”
Written by Joe McCoy
Vocal by Amy Irving
“Merry-Go-Round Broke Down”
Written by Cliff Friend and Dave Franklin
“Smile, Darn Ya, Smile”
Written by Jack Meskill, Charles O’Flynn and Max Rich
“Witchcraft”
Written by Coleman and Leigh
Performed by Frank Sinatra
Courtesy of Reprise Records
By arrangement with Warner Special Products
“Why Don’t You Do Right?” - Jessica Rabbit sings this in the Ink and Paint club
“Merry-Go-Round Broke Down” - Roger sings this in the bar right before Judge Doom shows up and tries to dip him
“Smile, Darn Ya, Smile” - This is playing as Eddie drives into Toon Town
“Witchcraft” - Not sure when this is playing, but not it…
-Dani
The third draft of the script I found say that they are playing a Tchaikovsky duet. Now I want to know because I know the piece sounds familure to me. Now I’ll have to go rent the movie.
–Anake “who’s obsessed with finding the answer as well”
Your’re all wrong. It’s Franz Liszt’s Third Hungarian Rhapsody.
Oh, and “Withcraft” plays when Eddie Valiant whips out a sword and it starts singing a la Frank Sinatra.
I just watched the movie and found the answer. Yeah, I was wrong (or the script I saw was wrong). The DVD I watched said it was Liszt’s Hungarian Rhapsody No. 2. It’s also on the Sony commercial with the woman walking the streets of New York and it plays when it shows the little girl jumping up and down. I think it was for a MP3 player.
–Anake
Number two? D’oh! Guess I can’t count today…