Rich, I think the reason that we are more sensitive to compression and other alterations in classical music is that most of us, and especially those of who regularly attend classical concerts, have a good reference of what orchestral instruments are supposed to sound like. Therefore we know when that "proper sound is not being presented. In pop music there is so much electronic altering of sound in the recording process that the right sound of any given instrument is not an absolute standard, but rather whatever the production team for that recording decides it should be. Not that I am knocking that process for the altering of the instrumental sound has become an art form in and of itself, but no matter how artistic it is, music produced this way cannot provide us with any kind of sonic reference. If there is no real "right" sound, then it is hard to know when something in the mastering, distribution or playback chain is making it sound "wrong." We can know if something sounds better or worse to us, but not if the sound is right or wrong. It is easier to hear the aberrations in a classical recording simply because we have a reference to compare that sound to.