Hi @d.c.palmer , re low frequencies and classical music - a lot.
It will take a bit of explaining to do here. But in summary, although a note of an instrument may have a fundamental frequency (e.g. your example of 40Hz) this is only relevant if it exists in time from minus ‘infinity’ to the future time ‘infinity’. Any notes start and stop and the act of this starting and stopping of notes broadens the bandwidth (measurement of spread of frequency of the note) to below and above 40Hz.
This leads to a lot of frequency content below any of the lowest fundamental notes of instruments in an orchestra, which perhaps helps partly explain why orchestral music is so difficult to accurately reproduce in a HiFi system at home and exactly why a decent sub bass helps.
If you follow my thread of ……https://community.naimaudio.com/t/english-premier-or-international-hifi-post-match-analysis/38767
You might find other interesting things there also.