So, I recently bought an oscilloscope and I decided to scope my keyboard. Check this out: here's some traces. The first is from setting 168 "SqrLead3". The second is from setting 164 "Ocarina". Notice anything peculiar? Is it just me or do those waves look awfully similar? (Spoiler alert: They're awfully similar"
So, yeah. Your fun fact of the day: the Casio CTK-2550 does not have a very good soundfont. Similar to this, "Whistle" is just a sine wave. And, well, in the synths, they have a bunch of "Square" and "Sawtooth" synths, but no pure square or sawtooth. I actually joked that the Ocarina setting was a better square wave than the actual square waves. But, hey, what do you expect from a $100 keyboard?