Have you ever tried to write down a piece of music for the piano?
Even if you are not a composer, this is a task from which you could learn a lot. Among other things, it will show you how there is always a variety of ways to do it, even if all you want to do is to write simple notes. If you want to include instructions of touch, articulation or pedalling, the complications grow even more numerous.
Through the centuries composers seem to have become more and more ambitious about this sort of thing – you only need to compare a score by Scarlatti or Bach with one by Debussy or Rachmaninoff to realise that. Of course, there are many exceptions to this, and one must not stop looking for all the subtle hints in early scores – this is the mistaken approach that led 19th century editors to feel the need to “fill in the gaps” left by their predecessors.
If you know where to look for them, a composer like Mozart certainly gives you all the hints you need to play his music like he envisaged it. If the score sometimes allows for different approaches, that is because he leaves that particular decision to you. In that sense, nothing has really changed over the years, except that it would seem that modern composers tend to leave less to the taste of the performer. But quite possibly that is also partly a misunderstanding. The composer of early music probably trusted his performers more because he (at that time, composers were sure to be male) knew that they would recognise the conventions of the particular time and place. Of course he hoped that his art would survive his own circumstances, but he wrote it down for people of his own culture, with roughly the same sort of references and education.
The composer of the 20th or the 21st century doesn’t belong to such a well-defined tradition. He or she often feels as if they are writing something entirely new, and for the whole world at once. Now, if you’re speaking to somebody on the other side of the globe about something that you just have invented, there are a lot more things to be explained than if you’re speaking to an old friend about a movie that you’ve both seen five times.
So, what do we learn from this?
Well, that it’s always important to look for the details of the score; that it’s important that you use reliable, urtext editions; that it’s important that you try to learn as much as possible about historical notation and performance practices. If you really want to understand a composer – Beethoven, Liszt, Chopin, Scriabin or anybody else – you need to reflect why they wrote their music down the way they did.