Chopin's music is frequently played with rubato, "the practice in performance of disregarding strict time, 'robbing' some note-values for expressive effect". There are differing opinions as to how much, and what type, of rubato is appropriate for his works. Charles Rosen comments that "most of the written-out indications of rubato in Chopin are to be found in his mazurkas ... It is probable that Chopin used the older form of rubato so important to Mozart ... [where] the melody note in the right hand is delayed until after the note in the bass ... An allied form of this rubato is the arpeggiation of the chords thereby delaying the melody note; according to Chopin's pupil, Karol Mikuli, Chopin was firmly opposed to this practice."
Who was something stolen from?
Mozart