Problem G1 Air

[ahfusaro]

The G1 Air user manual says verbatim:

Appendix
Troubleshooting
The pitch or tone of the piano sounds wrong in some
key regions
The G1/G1 Air’s piano sounds replicate the sound of an
actual piano as faithfully as possible. This means that in
some regions of the keyboard, you may feel that certain
overtones seem stronger, affecting the pitch or tone. This is
not a malfunction.

Please, is there anyone who can tell me concretely what he refers to exactly?

[bpoodoo]

We can't know exactly what the manual author refers to. Piano notes that sound out-of-tune could be a result of:

* The general phenomenon of pitch being subjective for sounds with complex harmonics (such as a piano)
* Pitch interpolation or extrapolation used when not all 88 notes have separate samples - most noticeable for notes in regions distant from the closest available sample at that pitch
* artifacts of the damper / string resonance modeling
* EQ or other built-in effects that change harmonic characteristics
* speaker effects that change harmonic characteristics
* cabinet resonances that change harmonic characteristics
* the pianos used to collect the samples may not have been perfectly tuned.

Probably there are many other possible reasons too.

And for what it's worth, I've never played a real acoustic piano that was perfectly tuned. But I did have a tuning wrench to adjust the tension in the individual string(s) for any note obviously out of tune. Perhaps future digital pianos might incorporate a digital model for "piano tuning wrench" for such fine-tuning.

[alexmu]

I'm not sure, but I suspect they could be talking about stretched tuning.
https://en.wikipedia.org/wiki/Stretched_tuning

Stretched tuning is a detail of musical tuning, applied to wire-stringed musical instruments, older, non-digital electric pianos (such as the Fender Rhodes piano and Wurlitzer electric piano), and some sample-based synthesizers based on these instruments, to accommodate the natural inharmonicity of their vibrating elements. In stretched tuning, two notes an octave apart, whose fundamental frequencies theoretically have an exact 2:1 ratio, are tuned slightly farther apart (a stretched octave).

It appears that this is related to the Inharmonicity of stringed instruments
https://en.wikipedia.org/wiki/Inharmonicity

In music, inharmonicity is the degree to which the frequencies of overtones (also known as partials or partial tones) depart from whole multiples of the fundamental frequency (harmonic series).

When pianos are tuned by piano tuners, the technician sometimes listens for the sound of "beating" when two notes are played together, and tunes to the point that minimizes roughness between tones. Piano tuners must deal with the inharmonicity of piano strings, which is present in different amounts in all of the ranges of the instrument, but especially in the bass and high treble registers. The result is that octaves are tuned slightly wider than the harmonic 2:1 ratio.

My Korg D1 manual has a similar warning to what you see in the G1 Air manual.
It also has the following note in the functions section.

About stretched tuning
In order to produce the most natural resonance, PIANO1 and PIANO2 sounds use a “stretched tuning” that makes the notes of the lower range slightly flatter than equal temperament, and the upper range slightly sharper. This is how an acoustic piano is normally tuned by professional tuners.

Perhaps the Korg manuals for D1 and G1 Air (and perhaps other models) are saying that the piano tuning and the relationships between harmonics are modelled on the tuning of real pianos, rather than a "correct" mathematical sequence of frequencies. People with digital instrument tuners, useful for guitar and other instruments, might conclude there is something wrong with the tuning, when in fact it's correctly modelling a real piano.