Today we were stuck a long time in traffic. We had Rachmaninoff on the stereo; those old recordings of Chopin waltzes, his own stuff and piano miniatures. After about two hours of Rachmaninoff's playing, you start to notice the really fine things he did with rhythm. He played rubato all the time, but it never sounds heavy-handed or out of place.
Interpretations from his time tend to have some bad fame as over-romantic and as having a distortion of rhythm unacceptable by today's standards. After listening to a lot of recordings from back then, I have to disagree. The rubato and his timing are so organic and natural, they seem to mimic the natural movements of our bodies, breathing or the rhythmic cadences of spoken language.
The more I listen to his Chopin waltzes, the more I am fascinated with all the little things he did, with extreme elegance and finesse. Some of them are so tiny they can't really be accurately described. No two phrases are the same. His interpretation of the waltzes is especially enlightening. He never stops with the rubato; not once. At the same time, the waltz rhythm is always there and is easy to follow. You can dance to it.
After that, a lot of modern recordings sound extremely unnatural -either too metronomic, or with a distorted unnatural tempo full of heaving and grunting- and when a ritardando or a smorzando or something similar finally come up in the score, they kill the rhythm. A lot of modern interpretations I have heard lack that grace and elegance that seem to be present in most recordings of masters from those times, like Hoffman, Horowitz or Rachmaninoff.
There is also the issue of the interpretation of the written tempo indications. It seems that we are taught today that ritardando means "getting slower", accelerando means "getting faster" and that things like slargando, slentando, stretto or smorzando are pretty much all variations on the theme. Many professional musicians and teachers don't know the difference between rallentando, ritardando or ritenuto; as well as how they all relate specifically to the work of different composers (even if all three appear in the same work, where they obviously mean different things!).
Once I am familiar with a score, when I listen to one of the great masters play it, I don't hear them interpreting all those tempo indications in terms of "slower-faster" but into concepts which are far more profound; "a slight hesitation", "elation", "alacrity", "impatience"; which they tend to do in a very subtle way. Piano or forte aren't "soft" and "loud" but become "far", "near", "whispering", "towering". Modern interpreters might be doing exactly what is written on the score, but being pedantic with the indications is not the same thing as giving deep thought to what they might actually mean, not only to the composer but to ourselves, in a more personal sense.
Striving for an organic sense of rhythm and a natural rubato should be something all musicians try to do. I think there is a lot to be learned from those old recordings. Not so much in the sense of what are they doing? but more in the way of why are they doing that?
Sadly it seems there isn't much thought put into the "why" these days; its all about hitting all the notes and some hazy generalizations people want to call "style".