Piano-and-data-nerds, rejoice. Now you can put everything you play into chart form. Using this tool on blog JoeyCloud.net, you can now chart pretty much any piano song by how often you'll hit any key while playing it.
For example, here's one of the most famous piano pieces out there, Beethoven's Fur Elise:
The longer the bar extending from a key (up for black keys, down for white), the more times you hit that key in playing a song.
One thing it tells you is how complex a song is, which can tell you something about how difficult a song is to play. The frantic Flight of the Bumblebee travels up and down the keyboard, hitting all sorts of chromatic notes along the way instead of just sticking to the notes in its key signature (A minor).
...while Chopsticks, the first song everyone learns on the piano, hangs in a range of less than one and a half octaves (and never strays from the notes of C major).
The tool allows you to chart any song, as long as you can find a MIDI file of it. What use is it? This might be one of those things that falls into the super-cool-but-with-little-practical-use category. But at the very least, maybe it can help you improve your odds of playing your next song correctly. For example, in Chopin's difficult Op. 10 No. 5, you can rest assured that hitting white keys will almost always be wrong.
(Then again, with a song nicknamed "Black Key Etude," maybe that's pretty self-evident.) Meanwhile, if you want to learn Billy Joel's Piano Man, stick almost entirely to white keys.
[h/t Flowing Data]