harmonsp

Verbatim presentation on the Tempo Rubato from Page 124 of the same book mentioned above:

No element in Chopin's style of playing has aroused more discussion than his celebrated tempo rubato and none, it is safe to say, has been more responsible for false interpretation of his music.............With whatever freedom Chopin may have 'leaned about with his bars', one thing is certain:his use of rubato was more restricted than is commonly thought and could never be reduced to a mere recipe for adding a novel flavor to the music. With him the give and take in the matter of time values which rubato implies was always subject to the discipline of the 'presiding measure'. In a considerable portion of his work the use of rubato is quite out of place and may even make nonsense of the music. The worst of all is to hear Chopin's phrases distorted by those clumsy accelerandi and ritardandi (within the space of a bar or two) which so often pass for rubato. Where Chopin himself produced wonderful effects of lingering, of hesitation or on the other hand, of eager anticipation, was in those passages where no harm is done to the rhythmic and harmonic structure if, over a firmly controlled bass, the player allows the melody to vacillate in response to the mood of the movement, to hover, as it were in the air, or to bound forward to meet the next accent.

.................................................. ...........................................
In another simple explanation I came across somewhere the use of rubato was wonderfully picturized as thus:

Imagine a beautiful tree (say in a yorkshire dale setting). When the breeze sets in, only the leaves quiver and the branches move, with no set pattern, while the trunk stand firm. The leaves and branches are likened to the right hand parts and the trunk to the firm bass of the left hand. This perhaps is the best explanation of Tempo Rubato as far as it can get. Good luck to those attempting it.