Complex sentence: This work is characteristic for the arpeggios played with the right hand, almost exclusively on black keys except in measure 66, where Chopin wrote an F-natural, the only white key for the right hand throughout the entire piece.
Split into simpler sentences: This work is characteristic for the arpeggios played with the right hand, that are almost exclusively on black keys. In measure 66, Chopin wrote an F-natural, the only white key for the right hand throughout the entire piece.