It was a bit like that in music, too, though not so extreme. All music students always learn basic theory and history, though not all schools take it very far. The young composers in one of the universities I attended seemed remarkably free of any association with the traditional craft of composition. I remember one concert that was a 'happening' where one of the performers fried pork chops while another sang cabaret songs. Ah, well...
But the truth of it is, as T. S. Eliot once remarked, no vers is libre to the poet who wants to do a good job. One of the most fundamental problems of composition is the melding of variety and unity. The great composers continue to astound us with how they achieve this. Let me send you back again to this post where I put up Bach's Goldberg Variations and Beethoven's Diabelli Variations. Bach did thirty variations on a simple air, every third variation of which was a canon at a different interval: unison, second, third and so on. The Beethoven is thirty-three variations on a silly waltz by Diabelli. Go have a listen, if you have time. My experience is that the wonder at what they did grows with each listening.
Variation form is just one way of unifying a piece. Other techniques have been developed. One of the most interesting is the fugue. You can't really speak about the form of a fugue the way you can of the form of a minuet or the form of a rondo as each fugue is really in a different form. What makes a fugue a fugue is not the form, but the texture. In a fugue a subject is presented which is answered in another voice, usually at the fifth. Typically all the voices enter with the same subject. Following this is an episode where elements of the subject and/or the countersubject (what the other voices are doing when one voice is presenting the subject) are varied and developed. In a normal entry, the second voice waits until the first is finished before presenting the subject, but another possibility is the stretto, where the subject is stacked up on itself. So, lots of unity in a fugue! The trick is to achieve variety.
Here is the subject and countersubject from the first fugue, in C major, from Bach's Well-Tempered Clavier, Bk 1:
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I said every fugue had a different form? This one is a good example. Most fugues have episodes of development between entries of the subject. This one doesn't. It has 24 entries of the one-and-a-half measure subject in a fugue only 27 measures long. How's that possible? The answer is stretto. He stacks them up. This is possibly the most strettoish fugue ever. Here is the first stretto:
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Stretto can cause problems of course: how do you know that stacking the subject on top of itself won't result in some nasty sounds like parallel fifths? Bach could apparently hear a subject and just know what strettos were possible. In any case, this one works fine a fourth below and a quarter note later. But there are a lot of strettos in this fugue. Here is another one:
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Starts with the same stretto, a fourth below and a quarter note later, but adds another a tenth below and three quarter notes later and yet another an octave plus a seventh below and five quarter notes later. In the actual fugue there are other voices playing as well. In order to show the stretto clearly I have left them out. Note that the last entry of the subject is irregular: a quarter note instead of an eighth rest followed by an eighth note. This is to avoid parallel octaves between the alto and bass. What Bach has done is layer together three more entries of the same subject before the first is finished!
I said all fugues were different? The very next one in the Well-Tempered Clavier, the C minor fugue, has no strettos whatsoever, but instead is a compendium of contrapuntal inversion. But that's a story for another day. Let's listen to the C major fugue. This is Friedrich Gulda playing both the prelude and the fugue, which starts around 2:09:
It is usually played a bit faster, but the slow tempo lets you hear everything very clearly.