In case anyone cares (and I know nobody actually does), here's the same passage from a real OPL3
. The high-pitched squeak is also there if you listen closely, but it's integrated in the overall sound and doesn't stick out like sore thumb the way it does with CQM.
Hmm, I noticed something when I did a frequency spectrum plot on those sample recordings:
Here is Cloudschatze's recording from CQM:
And here is NewRisingSUn's recording from OPL3:
The marked peak above 10 kHz are the "high pitched noises". The funny thing is, they are present in both recordings, but on CQM they occur around 12.4 kHz (and are easily detectable), while on the real OPL3 they occur at about 16.5 kHz, on the brink of the spectrum an adult human is supposed to hear.
I cannot hear the OPL3 noises on my speakers, because they are far too cheap and nasty to reproduce sounds that high, but I can make them out with my headphones when I turn the volume up a bit.