Beethoven 6 shows Beethoven more or less inventing a new way of composing- something none of his earlier symphonies actually did.
Music of the generation before Beethoven was composed in a highly rhetorical manner. Musical ideas interact with each other in patterns similar to those we encounter in language- the most common of which is your classic antecedent/consequent phrase structure.
All of Beethoven’s first five symphonies basically deal with musical ideas using tools learned from Mozart and Haydn. The difference is not in how Beethoven works with ideas, but in how long (the 3rd symphony) or how intensely (the 5th).
In the 6th, Beethoven moves decisively away from musical phrases structured around linguistic models- instead, the models in the processes of nature. Musical materials are developed in a whole different way. Instead of using the rhetorical techniques of fragmentation, imitation, augmentation and so on, Beethoven mostly works with layers of repetition and evolution. Some listeners who don’t “get” this piece complain that it is boring- this is because they are used to a more concise way of building music. The 5th (particularly the first movement )is, in fact, one of the most extreme examples of a “tight” approach to composition in all of music- there is no moment that doesn’t carry the music forward.
The 6th, on the other hand, is happy to keep us waiting- nature moves at her own pace. There is a fascinating passage in the development of the first movement at letter D. Beethoven builds a huge passage on the repetition of a one-bar long motive, which he never develops or modifies. Instead, he has a 24 bar crescendo in 4 bar long harmonic blocks to a fortissimo which takes 16 bars to dissipate. The only outcome of the passage is that he starts in Bb and ends in D. Then, completely breaking all remaining rules of composition, he repeats the entire 40 bar chunk of music but now moving from G major to E major, which is a very strange place to end up in a movement in F major. The mere fact that in this F major work you have Beethoven repeating and E Major chord for 16 bars is so radical compared to anything he’d ever done up to that time as to be almost beyond comparison in musical history- we’re talking Rite of Spring level of scandal, but there could have been no Rite without the Pastoral.
c. 2006 Kenneth Woods