(found this old post when doing a search on topic = classical)
A few comments:
(a) the interval from 16 kHz to 20 kHz is only two whole notes or four half-notes (B9 = 15804 Hz to D sharp 10 = 19912 Hz), which is a pretty small range. Especially since there are only "overtones", not fundamental notes of any common acoustic instrument, in this range.
(b) many audiophiles and music fans, depending on their age and gender, probably can't hear anything above 16 kHz. If that worries you, consider that many of the greatest performances of classical music are by artists or conductors who were presumably missing that range at the time of the performance. (And let's not even think about Beethoven's later compositions
(c) Quoting Iron Dreamer "Acoustic instruments have harmonics that can extend far above the generally accepted human hearing threshold of 20kHz, so it is more likely that overall sound quality could be limited by the frequency of redbook audio CD's."
Following up on that thought, frequencies above 20kHz could affect perceived "sound quality" only if human hearing extends above the generally accepted human hearing threshold. I've read that there have been tests of human hearing where a tone of about 30kHz is played at 20 or 30 dB higher (100 to 1000 times the power) than typical SPLs for harmonics of acoustic instruments, with never a positive result, i.e. absolutely no recognition that the 30 kHz tone is "on" vs. "off".