I hope instrumental music has a frisson live that recordings can't capture, even if it's not as immediately obvious as it might be with theatrical music.  Maybe cinema, TV and recordings have made people forget what it's like to be captivated by live performance.

That's not limited to "cultural" performance, by the way.  The few times I've seen live sport I was struck by how much more dynamic and exciting the experience was than watching it on TV.  I saw a gymnastics practise day at the 1996 Olympics and was amazed that despite not having a great seat (and not having close-ups/slow-motion/different angles) it was far more breathtaking than watching on the TV ever is.

There's a category to filter into this debate that I worry is becoming more and more marginalised nowadays (but I might be wrong) - recorded music (using electronic sounds or otherwise) designed to be played in a space (i.e. not just listened to on a CD). How often do any of the classic electronic works get 'live' performances these days?

And then there's sound art....

I think I've mentioned before The Onion's description of the walkman (on the 1980 page of Our Dumb Century) as a "population-pacification device".  Insidious things - the people who regularly use them think they're in control of choosing what they particularly want to hear, but often end up turning their favourite music into background noise as they travel, read, eat, shop, whatever.

Maybe one way for people to learn to listen better is to learn to appreciate silence rather than fear it.  But how do you do that?

The classics like Gesang der Jünglinge and Kontakte (and I suppose Mikrophonie counts as well) get plenty - their logistical requirements are pretty straightforward nowadays even relative to concert music. 

Yes indeed, and sometimes you can't go anywhere without bumping into Harvey's Mortuos plango.... Xenakis' tape pieces have pretty wide currency too, and of course the GRM people in Paris are constantly presenting their stuff old and new. What you don't see as often as when I started going to such events is concerts (as opposed to things like installations, where the audience may take its own time as in a gallery) consisting only of fixed-media pieces. Although I did go to such a concert only a couple of years ago, and greatly involving it was; of course no domestic reproduction system can reproduce the sound of a well-adjusted multichannel system in a concert hall, leaving aside the experience of being in an audience which I think is also an important factor in listening.