Did Shostakovich steal the catchiest thing he ever wrote...
... - i.e. the opening of his fifth symphony - from the finale of Stravinsky's Apollo? You decide.
https://www.youtube.com/watch?v=l87nzxY-yrI&list=PL14C60130BE7035E5&index=3
Also, the mordents that immediately follow the opening of Shostakovich's symphony seem to me clearly derived from the "Pas de deux" from the same ballet - which in turn, as I've said here before, seem to me clearly derived from Léhar's "Wie die Blumen im Lenze erblüh'n" from The Merry Widow.
https://www.youtube.com/watch?v=RBzXIzL5IL8&list=PLkcjStP9r6wIZfmqWvAUB1SrjJfFom5ol&index=8
https://www.youtube.com/watch?v=wKVYURuV0kM&list=PL5YJKMcT6TxdGPp2WICAYuX6s9yCk5zsZ&index=12
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