Chopin's harmonic innovations may have arisen partly from his keyboard improvisation technique. Temperley says that in his works "novel harmonic effects frequently result from the combination of ordinary appoggiaturas or passing notes with melodic figures of accompaniment", and cadences are delayed by the use of chords outside the home key (neapolitan sixths and diminished sevenths), or by sudden shifts to remote keys. Chord progressions sometimes anticipate the shifting tonality of later composers such as Claude Debussy, as does Chopin's use of modal harmony.
Who wrote about Chopin's "novel harmonic effects"?
Temperley