It is correct that Haydn was producing a lot of music,
mainly because this has been his job: Haydn was employed by the family Esterházy as court musician for 30 years. This meant he received a salary and was thus responsible and able to focus on music and composition at the court. E.g. of Haydn’s symphonies almost all (except for the 12 London symphonies and a few early ones) were written in this time. So this turns out to maybe 3 symphonies a year.
Yes, Haydn produced a lot of music. 107 symphonies sounds like an incredible amount, especially comparing to some 9 by Beethoven. But you need to keep in mind that at Haydn’s time a symphony was less complex in length, orchestration and structure. A typical Haydn symphony takes 15-30 minutes and uses a pretty small orchestra (in fact Haydn more or less standardized the “typical” classical symphony orchestra).
So three about 20 minutes symphonies per year is not really that unrealistic.
And then you get tools. The tools of a composer are not software or something. It is style and theory. Music (especially old music) was always bound to stylistic convention and rules that were taught to musicians and composers. People are amazed by 12 year old Mozart writing operas. But what this really shows is that having learned the tools and rules enables you to write decent music.
Especially pre 19th century music is very much defined by forms. Composers had some “standard schemes” they knew to work with the people. Musicians often joke that pop music always sounds the same, but actually baroque as well as classical music can very much be considered something like pop music of their
time (although a bit more complex maybe). And composers got away with composing music that kept to a recipe because there were no recordings in the time and people were generally less keen to always listen to the same pieces in concert. So what you have is a world where people listen to a lot less music than today, but go into concerts much more often and have a desire to hear new compositions. But this lessens the need for each composition to be very distinct.
Now, for classical form actually most of this was developed and popularized by Haydn and CPE Bach.
Starting with 19th century things start to get bigger. Orchestration turns from “use the 10 instruments you have” to “combine this big orchestra of (say) 30 instruments to get exactly the texture you want”. The experts on orchestration often were conductors, because they knew the orchestras, and composers would often consult conductors and players to get the right orchestration (Brahms famously employed Hermann Levy as orchestration help). Compositions get much longer, and people have enough of the formalism of classical court music. On the other hand the focus of music shifts from nobility to the middle class.
This results in composers needing much more time for composition and fewer, larger pieces. But what remains is that composer hat rules and tools under their belts that made this possible. The rules had changed, the tools had changed. The first big treatise of instrumentation was published in 1844, for example.
Now, what are the tools available to a composer today? We know lots of rules, and styles, but probably not as well as the people who used them. And we have different expectations to satisfy. A composer nowadays could spend a lot of effort to try to replicate what the master of the past perfected. He will need to compete with the masters of their time and in the end people might not even want to hear it. Composers nowadays are expected to not compose the same stuff that was composed 200 years ago. Due to a long history of music public focus has shifted from experiencing new compositions to doing something from a legacy of may centuries of music. And due to recording technology a composition will need to standout among a massive catalogue of ready available music.
And nowadays we have software. And that is nice. It is much easier to do macro-planning with software, where you can easily change things, insert stuff, remove stuff, copy stuff. It is not really easier to write than pencil and paper though. Software nowadays has playback, and that can be nice for e.g. checking chords or something. But by necessity the software playback is not going to sound like the real thing. So a composer will still need to be able to imagine how something would sound. The playback might help. It might also lead you onto the totally wrong track. And this might even negatively affect the quality of the composition. Many modern composers thus still prefer working with pencil and paper, using software playback just for checking, not for composition. And this means that the core tools a composer needs — theory, the ability to imagine how something sounds, creativity — are the same as they have been.
