Why is On-screen piano (F4) 1 octave lower than it should be ?

[Josdams]

Is there a particular reason for it ? or is just a mistake?

According to the rules (https://en.wikipedia.org/wiki/Piano_key_frequencies) we should be getting accurate frequency representation but currently when you play C4 you are actually hearing C5.

Do you have idea of how many people get confuse because of this ?

[huggermugger]

Some devices use C3 as Middle C, others use C4. It's a confusion that started decades ago when MIDI was first being implemented. But whether it's C3 or C4, there's no correlation between the note number and the frequency. For example, if you raise the octave setting of a Subtractor patch by a couple of octaves, the pitch you hear from C3 will be two octaves higher than what you might have expected.

[selig]

On the chart, which I’ve used for years btw, middle C is MIDI note 60. This never changes, middle C is always note #60 and always 261.6256 Hz so use this (and not the octave) as your ‘stable’ note reference.
The octave naming debacle from early MIDI days is still causing headaches today…