It’s very subtle; I don’t associate it with a particular instrument, but rather with how Pianoteq works. I imagine it has to do with the stereo field management. I notice it especially on long notes in the middle register. I haven't searched the forum for this topic yet; maybe it’s already been covered, I don’t know. It’s not that it’s terrible, but the truth is it's there, and it’s somewhat unsettling to hear a hint of vibrato on a piano (the normal thing would be to hear amplitude oscillations, which are standard in an instrument with several strings per note, that sort of chorus effect typical of a piano).

Actually, there are so many factors that could be at play (string inharmonicity, the interaction between strings of the same key, the hammer strike, etc.) that, as we say in Spanish, the only thing for sure is that who knows.

But the strange thing about the whole matter is that we don't perceive it through headphones...

If I connect headphones to the iPhone, the piano sound (Bösendorfer) is perfect.

However, if I connect speakers (M-Audio), while playing I hear some notes that sound out of tune, with a tone that oscillates like a wave.

Has anyone else experienced the same issue?

Thanks