Does greatness always involve being revolutionary?That is a really interesting question that gets more and more interesting the more you look at music history. The idea that greatness in music is somehow associated with being "revolutionary" really began with Beethoven and one piece in particular, his Symphony No. 3, "Eroica" that was originally inspired by Napoleon. Once Napoleon proclaimed himself emperor, he lost lustre in Beethoven's eyes and he scratched out the original dedication:
Another very interesting element is that the Symphony No. 3 of Beethoven not only paid hommage (originally) to a politically revolutionary figure, it is also, or is usually described as, a revolutionary work in terms of its musical structure. Wikipedia gives the standard view:
I suppose I could attempt to revise this conventional wisdom, (for example, the Beethoven Symphony No. 3 is about 54 minutes long in most performances, while Mozart's Symphony No. 41 is around 44 minutes long--not very much shorter) but that would be the subject of another post. For now, I just want to point out the fusion of two different ideas of "revolutionary": one is political, relating to the progressive ideals of the French Revolution while the other is musical, relating to the length, emotional intensity, and structural innovations of the piece. Note that I am not necessarily accepting this as given, but pointing to how the work has been received.The work is a milestone work of classical-style composition; it is twice as long as the symphonies of Joseph Haydn and Wolfgang Amadeus Mozart – the first movement is almost as long as a typical Classical symphony (with repetition of the exposition). Thematically, it covers more emotional ground than Beethoven's earlier symphonies, and thus marks the beginning of the Romantic period in classical music.The second movement especially displays a great emotional range, from the misery of the funeral march theme, to the relative solace of happier, major-key episodes. The finale displays a similar emotional range, and is given a thematic importance then unheard of. In earlier symphonies, the finale was a quick and breezy conclusion; here, the finale is a lengthy set of variations and fugue on a theme from Beethoven's music for the ballet The Creatures of Prometheus (1801).
So, for 19th century composers (the Eroica was composed in 1804) Beethoven was their perfect model of the great composer. Every 19th century composer, to some degree, modeled themselves after him. Therefore, the idea that a great composer was revolutionary--in both senses of the word--became an integral part of the model. A composer, any artist really, should, if they follow the standard model, be not only technically progressive, but politically so as well.
But how universal is this model, really? Not so terribly, in fact. Prior to Beethoven it is hard to find a single example of a composer who is great because of being both technically and politically progressive. You could argue that the most technically progressive composers prior to Beethoven prominently included C. P. E. Bach, Joseph Haydn, Domenico Scarlatti, Antonio Vivaldi, Giovanni Gabrieli and Claudio Monteverdi. But none of these had the slightest politically progressive profile that I know of. They all worked for establishment figures and institutions and were to no discernible extent, dissidents.
There have even been composers since Beethoven, though not in large numbers, who could easily be characterized as not progressive or even conservative. Among these one of the most prominent would be Johannes Brahms who, ironically, wanted to return music to the kinds of aesthetic procedures followed by Beethoven instead of the more radical methods of Liszt and Wagner.
In the period of high modernism, from around 1900 to sometime in the 1960s, technical progressivism almost seemed to overshadow political progressivism, though there are certainly composers who continued to fuse the two ideas such as Cornelius Cardew, Luigi Nono, and Frederic Rzewski.
More recently it seems likely that most composers, with an eye to not alienating any potential audience members, tend to mildly support all the widely accepted "causes" of the day such as climate change, anti-racism and so on. But the idea that a "great" composer has to be both politically and technically revolutionary seems to be fading. The most prominent American composers these days, who would likely include Philip Glass, Steve Reich, John Adams and John Luther Adams, seem to be particularly strongly progressive neither politically or technically. All have returned to some form of tonality, for example.
So there you have it. The answer to the question is "no", but for a while it was pretty common. As our envoi the likely choice is the Symphony No. 3 of Beethoven. This is Lenny conducting the Vienna Phillies: