Yes, no. 3: during Szymanowski's lifetime, it became a little bit too popular, and he grew to hate it, a little bit like the moonlight sonata for Beethoven.

In terms of difficulty, I'm not the best person to ask, because I get everything out of proportion. What's comfortable for me might be less so for you, and vice versa. For me, composers such as Mozart, Chopin, Rachmaninoff, Scriabin are very challenging (although I love their music). I find Brahms, Debussy, Szymanowski, Sorabji much more natural, even though other people tell me those composers are considered "difficult". I've only played a couple of etudes each from Rachmaninoff and Scriabin (although lots of other Rachmaninoff that's not piano solo, e.g. the song accompaniments, cello sonata, two-piano versions of concerti).

For me, Szymanowski falls under the hands very well; the technical challenges are more in the direction of sorting out the layers, voicing and pedalling rather than power and agility. Opus 4 is towards the easier end of the scale; there is some much more difficult (and spectacular and rewarding) piano writing in the Masques, the Metopes, and the third sonata.

These were very nicely played . Your piano sounds nice and clear, and your "tops" are nice and focussed, so each chord had a nice bright, crunchy sound. I liked also your orchestration of the different lines and textures in each one. They must have taken quite an effort to learn! I heard these once a few years ago on the radio, played by Martin Roscoe, and I especially liked No 3 in the set (which seems to be the most well-known of the 4). How do they compare e.g. to the etudes by Rachmaninov and Scriabin? And how do they feel "under the hands"?

Anyhow, keep well!

thanks to your sample program i was able to run the example and to generate an mp4.  i did have some problem with getting the titles in the movie (there was a complaint about ImageMagick and convert not found, although certainly i have it and use it all the time), but that's not a big deal, the animation is the main point.  thank you for sharing your work and time.

https://imslp.org/wiki/Category:Szymanowski,_Karol

The 9 preludes, opus 1 are probably the best place to start if you want to have a go at playing something.  Or look for recordings of the orchestral music.  The violin concertos are amazing!

The visuals are all home-made using the Python programming language.  I'm afraid I haven't put much effort into making it easy to use for non-programmers, but if you're interested you can find my code at https://github.com/hanysz/midi_python_animations

This has been a long time coming.  I learned number 3 last century, but the others in the set are a bit more challenging!

Thanks Alexander for sharing this true marvel !

What software do you run to make the visuals with drops, stars and circles ? (a marvel for the eyes too!)

https://youtu.be/32m6bMdD0NY