Chopin’s music is well known for benefiting from rubato (which was how he himself performed his music), as opposed to a strictly regular playing. Yet there is usually call for caution when the music is performed with wobbly, over-exaggerated, inappropriate “rubato” (e.g. attempting to justify insecure playing, with reference to expressive rubato).

His playing was always noble and beautiful; his tones sang, whether in full forte or softest piano. He took infinite pains to teach his pupils this legato, cantabile style of playing. His most severe criticism was “He—or she—does not know how to join two notes together.” He also demanded the strictest adherence to rhythm. He hated all lingering and dragging, misplaced rubatos, as well as exaggerated ritardandos … and it is precisely in this respect that people make such terrible errors in playing his works.

— Friederike Müller, “From the Diary of a Viennese Chopin Pupil”

However, while some can provide restrictive quotes about Chopin such as the above, often to the effect that “the accompanying hand always played in strict tempo”, these quotes need to be considered in better context in terms both of the time when they were made and of the situations that may have prompted the original writer to set down the thoughts. Constantin von Sternberg (1852–1924) has written:

It is amusing to note that even some serious persons express the idea that in tempo rubato “the right hand may use a certain freedom while the left hand must keep strict time.” (See Niecks’ Life of Chopin, II, p. 101.) A nice sort of music would result from such playing! Something like the singing of a good vocalist accompanied by a poor blockhead who hammers away in strict time without yielding to the singer who, in sheer despair, must renounce all artistic expression. It is reported by some ladies that Chopin himself gave them this explanation, but – they might not have understood him [...]

— Constantin von Sternberg (1852–1924), Tempo rubato, and other essays

There are also views of contemporary writers such as Hector Berlioz.

This suggests that Chopin is not to be found at commonly encountered one-sided extremes. The unbalanced views are:

• that Chopin requires metronomic rhythm in the left hand;

• that insecure performances of Chopin can be justified with reference to rubato;

• that performances with particular inflections, that result from technical limits/insecurities rather than a performer’s intentions, can be justified with reference to rubato.

Some performers’ (and piano-schools’) “too strongly held one-sided views on Chopin’s way of playing rubato” may account for some unsatisfactory interpretations of his music.

Source: Wikipedia