Here’s a big difference between classical music, and pop music of the rock era — rhythm. Not that classical music doesn’t have rhythm, but rhythm functions very differently in it. In classical music, rhythm is analyzed as a structural element of music. To repeat the same rhythms, over and over, is considered very crude. Rhythmic patterns are supposed to change and develop. To understand the rhythm of a piece, it’s enough to study a score. You can see what the patterns are, and how they change and develop. The identity of the music — and a lot of its value — lies in the score, in elements that can be written down and fixed for all time.
In pop music of the rock era, none of this is true. Rhythm is (among other things) a “groove” — a way of inflecting rhythmic patterns, so that even simple, repeated rhythms can be changed in ways that make them not simple at all. The drummer in a rock band might push the beat forward, playing always a little bit ahead, while a sax solo might lag sexily behind. Meanwhile the singer (just listen to James Brown!) can dance around the beats, getting ahead of them, playfully falling behind them, and often landing in the cracks between. Pop musicians (and jazz musicians, too) know exactly what they’re doing with all this; they do it purposely.
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.
Far-reaching footnotes: First, rock and jazz — with their stress on groove and body language — were a musical eruption of non-western culture (some aspects of it, anyway), in the heart of the west. That’s a profound change, and helps explain some of the more flagrant attacks on rock during the ’50s. Was rock the end of civilization? (Or, as some southern sherriff put it, was it “negro [not quite the word he used], Communist music”?) No, but in many ways it was one forward-looking nail in the coffin of western dominance.
Second, classical music didn’t always have the free play of beat-lengths that it has now. At least in one famous 19th-century book on singing (Manuel Garcia Jr.’s L’art du chant), singers are told that they can freely change the rhythms of what they sing, but that the accompaniment is going to keep a steady pace. In other words, when a singer pushes the beat, going up the hill toward a climax, the orchestra will keep on playing those Italian opera oom-pahs without any change. Nowadays, one mark of a good opera conductor is his or her ability to move the orchestra along with a singer — but apparently this isn’t what happened 150 years ago.