I don't know anymore. I thought my hearing was getting worse considering my wife and daughter can hear higher frequencies that I can't even detect now (as I'm getting older).

I have a Yamaha PSR S-700.., and my ears must be more in tuned to the piano than I thought. Several notes in the lower register (just below middle C) in the default grand (and several other pianos) have an issue that my ears really seem to be tuned into.

These notes suffer from a very notable loop point that also has a negative sonic reaction with the preset decay of the notes. When added to a few other adjacent notes (these individual keys) can sound a little out of tune. I've also noticed that problems with these notes arise when sustaining them as well.

It's worsened by the keyboards default EQ settings too. The only way I've been able to put it within tolerable levels is to do some heavy EQ'ing to get a better balance.

The keyboard isn't defective either. It's functioning properly..., but for some reason my ears appear to react to these particular notes that appear to suffer from sample stretching, and other sample related issues.

I'm also wondering if it's possible that the S-700's speakers (and cabinet design) might amplify the problem more. I've been doing a lot of testing by completely flat-lining the EQ and working up from there.