Byron Janis plays Chopin's "Grand Valse Brillante", Op. 18 

Video footage of Byron Janis sharing his discovery -- in 1967 at a chateau in France and also five years later at Yale University -- of unknown versions of two of Chopin's more famous waltzes: the G♭ major, Op. 70, No. 1; and the Grand Valse Brillante in E♭ major, Op. 18.
Janis gives examples at the keyboard of subtle and significant differences among the versions and performs the Opus 18.