The machine on which Conlon Nancarrow created his player piano rolls. Photo by Carol Law, 1977. Collection: C Amirkhanian.
In 1947, the composer Conlon Nancarrow—frustrated with human pianists and their limited ability to play his rhythmically complex music—purchased a device which allowed him to punch holes in player piano rolls. This technology allowed him to create incredibly complex musical compositions, unplayable by human hands, which later came to be widely recognized by electronic musicians as an important precursor to their work.
A similar interest in seemingly impossible music can be found today in a group of musicians who use MIDI files (which store musical notes and timings, not unlike player piano rolls) to create compositions that feature staggering numbers of notes. They're calling this kind of music "black MIDI," which basically means that when you look at the music in the form of standard notation, it looks like almost solid black:
Blackers take these MIDI files and run them through software such as Synesthesia, which is kind of an educational version of Guitar Hero for the piano, and bills itself as "piano for everyone." It's kind of brilliant to imagine a novice piano player looking for some online tutorials and stumbling across, say, this video of the song Bad Apple, which reportedly includes 8.49 million separate notes.
That version of Bad Apple is by a notable blacker who goes by the name TheSuperMarioBros2; as you might infer from the name and the choice of song, video game music plays a big role in the black MIDI scene.
There's a nascent wiki for the black MIDI community, where you can find links to more of these videos, if you'd like to continue on down the rabbit hole...