Sometimes I forget what a genius Mozart was. I don't get to play much of his music, frankly; we spend a lot more time with later composers like Shostakovitch and Tchaikovsky and Debussy, wonderful composers who happened to write music that's bound to get your heart pounding with joy or anger or righteous indignation regardless of how much you know about classical music. When I took music theory in college, I was always incredibly impressed at the remarkable amount of structure that composers have within their pieces. A truly great piece of music often has intricate details, chords that mean certain things or cadences that only resolve once in an entire piece or what have you, that are mostly lost on modern listeners. Hell, I don't hear this stuff, or at least not frequently or consciously. But it's like writing, there are threads reaching out all over connection parts of the piece that give it cohesion.
Anyway, it tends to be easier to hear this in later composers, maybe because they started assuming we all didn't know shit, I'm not sure. I mean, it's pretty easy for most people to hear a melody and connect it with an image (like Berlioz's idee fixe or Strauss's tone poems) as long as they've read their program notes and are paying attention. But do we really hear it anymore when Beethoven throws a "wrong" chord in at the end of a cadence in one of his symphonies? Because when he wrote it, that pissed people off. The man was a rebel with all that wrong-chord shit. And Haydn wrote tons of music jokes into his pieces that make me giggle when I listen to them, but all most people remember is the Surprise Symphony.
Anyway, I'm getting off topic. I like playing older music, like Handel and Mozart, partially because it's so tightly structured that when they do something different it's fabulous, like a victorian lady musician suddenly starting to do a striptease on her piano (one of the only instruments ladies were allowed to play in that era because it placed them in profile to the audience instead of face-on). It's unexpected, and I have to chuckle and say "Damn, Haydn, way to rock the boat!". But right now I'm playing Mozart's 41st Symphony with a not-incredible orchestra and just relishing all the little details. Mostly it's just fun and games until the last movement, when he suddenly starts bringing everybody in with the same melodic figure but at all kinds of different parts in the measure. And damn if it doesn't work out. And then, in the fabulous coda, every theme from the whole symphony comes back all at once, all played together and you suddenly realize that they all fit together. And all I can think is my god, Mozart was a genius, he was planning this all along! And I wish everybody in the audience could feel the way that makes my heart pound.