Complex sentence: The mistake was the first of its kind in Oscars history for Best Picture, though, in 1964, Sammy Davis Jr. read out the wrong winner for Best Music Score after being given the wrong envelope.
Split into simpler sentences: The mistake was the first of its kind in Oscars history for Best Picture. The only other time this type of mistake had occurred was in 1964, when Sammy Davis Jr. read out the wrong winner for Best Music Score after being given the wrong envelope.