In the Charles Eliot Norton lectures, Leonard Bernstein analyses Beethoven’s 6th Symphony, and highlights one of Beethoven’s greatest strengths as a composer:

[The 6th Symphony] exemplifies that special molecular growth process of his, the incredibly ongoing quality of his music, whereby motifs, or parts of motifs, can become attached, or detached, in infinite numbers of ways, by constant repositioning, conjoining and embedding. And this process is so intense and diversified, that even so apparently destructive an activity as fragmentation contributes profusely to the growth of this living organism. [It is] a constant metaphorical growth, self-generating, always on its own track…

This ‘organic molecular’ quality is evident in everything that Beethoven wrote. I sometimes think of his work as the audible equivalent of a Mandelbrot set, because it shares a similar ‘self-similarity‘, ie the whole has the same shape as one or more of the parts.

Image of Mandelbrot Set from Brady Fractals

For example, as Bernstein points out, the I-V (F-C) relationship that occurs in the bass during the first four bars of the piece, re-occurs throughout the symphony in various different guises, whether it’s augmented, diminished, retrograde, inverted, etc. On a much broader level, the key structure across each movement, and even the entire symphony, can also be explained as a tonic-dominant relationship.

It is Beethoven’s genius that he controls this ‘molecular organic’ system so well, but it wouldn’t have been possible without the miracle of the tonal system and the sonata structures that he worked with. I’m of the opinion that genius is a coincidence of person, place and time, and that all three need to be in harmony for masterpieces to emerge. To my mind there’s no doubt that Beethoven, and Mozart before him, were perfectly placed to exploit the tonal system when it reached its zenith in terms of expressibility, in the late 18th and early 19th centuries.

I’d go so far as to say that there has never been a more powerful expressive force in all art than tonality and the sonata form in music, and no-one used these forms more successfully than Mozart and Beethoven. This is why either one or other of them is usually considered, by the most knowledgeable and sane music lovers, the greatest musician of all time. Bernstein plumps for the title going to Beethoven in his book The Joy of Music (‘Let’s just say it out, unashamed: Beethoven is the greatest composer who ever lived!’). I vacillate between the two, depending on which one of them I listened to last. But, with the possible exception of JS Bach, no-one else can challenge them.