If you've ever been concerned about sound quality on recent recordings of popular music, especially on mp3 files, you should definitely check out Robert Levine's The Death of High Fidelity in Rolling Stone, which spells out the technical reasons for audio compression--the practice of ironing out dynamic levels at the expense of sonic image and detail.
Might the reason for classical music's newfound popularity be as simple as a reaction against the bland audio quality of many popular releases in favor of listening to a genre of music that contains both loud and soft sections?
Consider one of my favorite recordings, Shostakovich's 8th Symphony as played by the Leningrad Symphony under Mravinsky. I find listening to this recording difficult unless I'm in a place and situation where I can appreciate dynamic contrasts that range from the tenderest transcendental sounds to the most terrifying, corpse-grinding Stalinesque volume imaginable from an orchestra.
Take a look at The Loudness War, a YouTube clip that focuses on the opening and drum entrance from Paul McCartney's Figure of Eight to demonstrate how compression can often ruin a recording that once relied on extremes of dynamic for its effect:
Then again, perhaps I'm wrong about all of this. Perhaps the reason why classical music is proving so popular these days is that it doesn't suck the way a lot of popular music does. I spent 20 years buying LPs and CDs of popular music, only to find that for the most part only two or three songs on an album were listenable and the rest were filler. Maybe that's why the downloading phenomenon is draining the profits of the recording industry. Back in the LP and CD ages, mediocre content could still move huge amounts of product as long as there were a handful of hits. Nowadays consumers bypass the dreck on albums and download only the handful of good songs, resulting in lower revenues.
Buy or download any decent recording of classical works such as Beethoven's Sixth Symphony and you'll be able to hear an album-length, high-quality work that you might not understand the first time, but will come back to in order to get more out of it. Over time, your understanding of the music will actually enhance your listening experience. Very few popular albums have ever risen to this level--Pink Floyd's Dark Side of the Moon and U2's The Joshua Tree are some that did.
Better yet, realize that recordings can give you but a taste of what the true musical experience is all about: the live performance, which is alive and well these days, as Jon Terauds writes in the Toronto Star. Whether you're listening to mp3's on an ipod or vintage LP's on a tricked-out audiophile system, the real deal is happens in the concert hall or arena, no matter what kind of musical style you favor. Spending the time and money to attend concerts can enable the experiences of live music that can be life-changing, and although the live music experience won't have the permanence of the recording, the ephemeral moments of the concert hall are often what we remember the longest, and with the most fondness.