Here's a fascinating article by Greg Sandow on rhythm:
But classical musicians often don't hear the groove at all! One reason for this is that -- especially in romantic classical music -- rhythms are stretchable. Imagine a melodic phrase that arches up toward a climax. Most classical musicians will push the beat faster as they surge toward that peak. They'll literally change the beats, pressing them closer together. Then, as they come down from the climax, they'll slow down. They may not know they're doing this; it's so much a part of classical performance that it's practically unconscious. And they may not be able to avoid doing it, even if they're suddenly thrust into a non-classical context where pulling and pushing the beats in this way isn't appropriate.
Here's a real-life example. I won't name names, but I know a terrific musician who works both in classical and pop. He's done some crossover projects, using pop musicians and classical musicians together, including some very big classical names. He told me once that one of the big classical names couldn't feel the groove. He'd push the beat forward when he reached toward the climax of a melody -- not really hearing the other players, who were grooving along, each in his own way inflecting what they infallibly felt as a steady pulse. What the classical soloist did in this case would be reasonable, if he knew he was leaving the groove, and came back to it after he'd pushed the phrase to its climax. But he couldn't do this, because he didn't feel the groove, or at least didn't feel it with the tight precision that the pop musicians had. He'd come back to a very slightly different tempo, which for the pop musicians was like not feeling any tempo at all.
One result of this -- some people, for whom classical music is home base, can't always hear what's going on in pop music. A classical musician might hear a rock song, and say, "Yuck! Those rhythms are just juvenile! The same pounding 4/4 in every measure." While a rock musician will say, "Listen to how tight they are!" -- meaning we should listen to how well they play their groove. Each good band has a groove of its own. Those different grooves help give different songs their identities -- something classical music people may not hear, because they're listening for structural things that just may not happen in rock. Meanwhile the groove is developing in ways they don't get at all.
To put this in another way (crudely stating an intriguing philosophical difference) -- classical music gets involved with thought, rock gets involved with body language. I'd say both are needed for a full view of life. But remember that this really is quite crudely stated; rock music in fact has thought, and classical music does have body langauge. It's just that the relative importance of thought and body language differs.
Interesting! I'd use his distinction in that last paragraph to explain the difference between the "classic" styles of Jewish music that I love and the "contemporary" JM styles I find banal. The new stuff is all about beat -- the melody is almost an afterthought.