1. Recording Technology
Rewind 100 years. Say you wanted to hear a decent performance of Bach. You would probably have to go on the right weekend to a big city. If you found that weekend, and had enough money to secure the tickets, and did so before they were sold out, you would then be in the extraordinary and rare position to hear a performance of Bach that would in no way resemble what Bach actually would have sounded like. Why not, you ask?
2. Performance Practice
Performances of Bach 100 years ago were rare, but they were also steeped in egregious error of performance. The tempos, orchestration, the very quality of the instruments, and, above all, the style of singing would be enough to have made Bach alienated and estranged in his own ears from what is his own composition. That is because music is not simply about what is on the page. Musicologists, realizing this, have spent the last century developing serious advancements in how to perform the works of a period distant from our own with accuracy, and this has allowed us, for the first time, to actually hear it in ways that would be recognizable to the composers themselves.
3. The Printing Press
But if you rewind 200 years, the sheet music of Bach would be nowhere found. It might be in a box in some palace or church or house or, later, museum, but it would likely be hand-written, never published. This is because at this time music was not rarely intended to be performed more than once after its composition. This changed for all sorts of reasons, but one of the main ones was the proliferation of sheet music. Music was some of the earliest printed stuff after Gutenberg’s revolution, but, still, it was unlikely that a publisher would spend that much money publishing works that were not modern and popular, until such a time as it became popular to like the non-modern stuff. Think about times before the printing press—how on earth was a church supposed to use old music if it had to have a trained reader travel hundreds of miles to a library to pay serious money to get a manuscript copied, at great length and labor, by a monk who might not let him see the manuscript beforehand anyway?
4. Economic Prosperity
Traditionalism requires a certain amount of economic risk, risk which would be unlikely to pay off in less opulent times. Today, to release an album of Bach, you need to rely on a market that likes Bach because you have to pay a handful of the most highly trained musicians in the world lots of money to record it. On top of this, the conductor is smart to have a team of musicologists researching the music and verifying the performance practice decisions. But imagine the risk of releasing a CD of Josquin or Regis. Sure, the world needs to hear them, but if you’re a recording label, you have to face the fact that the world has never heard them. Investing money in old dead composers people have never heard of is just less of a financial priority than investing in living ones. I complain as much as anyone that the Tallis Scholars pander to their client-base of people lustful for angelic choir-boy music at the expense of accuracy, but that is an eminently first-world problem. Not only should other centuries have not worried about traditional music, but they could not on any meaningful scale.