I know Ethan is very scientific. It so happens that I'm picky when it comes to assigning octave numbers. Scientific Pitch Notation places C4 as middle C ~262Hz. That being said, the image on p.28 has 1000Hz labeled as 'B6' despite that referencing middle C as 'C5'.
B4 ~ 494Hz
B5 ~ 988Hz
B6 ~ 1976Hz
So, besides being the wrong octave, it also doesn't mention that the note played is actually sharp. There is no 1000Hz when A=440Hz - no matter what octave you call it.
But Ethan probably didn't write that software. Just thought I'd mention it!