One posthumously published piano piece by this composer opens with a G-sharp octave in the left hand and features persistent four-against-three rhythms in its C-sharp minor outer sections. The nickname of another work by this composer is due to the repeated A-flats that continue through most of the piece. The poetry of his countryman Adam Mickiewicz is said to have inspired his four ballades, and this composer wrote Fantaisie-Impromptu and the "Raindrop" Prelude. The dance music of his home country inspired his mazurkas and polonaises.  For 10 points, name this Polish composer of many waltzes 
One posthumously published piano piece by this composer opens with a G-sharp octave in the left hand and features persistent four-against-three rhythms in its C-sharp minor outer sections. The nickname of another work by this composer is due to the repeated A-flats that continue through most of the piece. The poetry of his countryman Adam Mickiewicz is said to have inspired his four ballades, and this composer wrote Fantaisie-Impromptu and the "Raindrop" Prelude. The dance music of his home country inspired his mazurkas and polonaises.  For 10 points, name this Polish composer of many waltzes and nocturnes for piano.
One posthumously published piano piece by this composer opens with a G-sharp octave in the left hand and features persistent four-against-three rhythms in its C-sharp minor outer sections.
Frédéric François Chopin