A lot of factors are involved in this, going back for years. I don't feel like writing another book-length post belaboring all the ills of the music industry (which could fill multiple books, were it all told!), but I'll add a few small personal observations:
In the past week, I've heard three people comment on how vinyl records are "becoming popular" now. First was a teenage student, who couldn't even remember (if he knew) what to call them; he just described them as "like big, black CDs." I happen to know his father has a nice system (good Harbeth speakers), but listens to CDs only. Incidentally, the kid himself has a lot of music, but no CDs. No LPs, either. 100 percent of his "collection" consists of (mostly free, illegal) downloads. He has more excuses for why that is okay than you'd ever think of, and cannot or will not think of it as "stealing."
Yesterday, I stopped at a small roadside stall that sells used records out of cardboard boxes. You can sit on low (about 1 foot high, if that) wooden stools and flip through the records in the boxes. New stock is put out at the beginning of the week, and prices for that day are $5 per record. Every day or two (depending on how much stock is sold) the price drops, until by Friday he remaining records cost only $1-2. So if you see something GOOD, you grab it the first day at the higher price, or risk losing it to someone else. Or you take your chances that no one else will want it, and come back in a day or two, to see if you can get it cheaper. There was a lady, I'd guess she was forty-ish, buying records. She asked the old lady there (who runs the sales, collecting the money on behalf of the owner, who has a regular shop nearby) about where to get records cleaned, explaining that she had just got back into spinning records again, and didn't know what to do... I talked to her (offered to clean a few records), and she was saying how more and more people just like her were getting back into records "just like in the old days."
Today I was back at the same place (beat out the high-level scavengers this week, and grabbed a couple Columbia 6-eyes and some other nice stuff!

) and while I was there, an old man came up to talk to the old lady there, and he, too, started saying how she must have a good business, because the old vinyl records were becoming popular, and the prices were going up, up, up on them.
How much of this is truth and how much is media exaggeration, urban myth, or something else, is anyone's guess. But it struck me that within less than a week, I had heard three ordinary people, only one of whom was actually spinning vinyl (and she was just starting out) SAY (without any prompting from me) that vinyl records were becoming trendy/popular/sought-after again. Three people from three very different age groups, and different income and age brackets, too. One of them was actually a living example of that trend.
Music sales --as in sales of new recordings by new artists through the traditional channels-- my be contracting, even dying, but interest in music perhaps not so. None of those secondhand vinyl sales are likely to be in any statistics.
I recently "discovered" Grooveshark. Actually, I'd known about it for a long time, but only recently finally tried it. I have to agree, it's a pretty convenient way to access a lot of music for background listening, etc... I also listen to a some streaming online radio stations. How much money does the industry make from any of this? Next-to-nothing.
In the next three months, I plan to go to concerts by Eric Clapton, Marianne Faithful, and the Eagles. That will put some money in those entertainers' pockets. But aside from concert ticket sales, how much money have I given them lately? Back in the 1960s through the beginning of the nineties, I bought viny LPs and then CDs by each of these groups. Since 2000, I've bought even MORE of their music than I did before then, but NONE of it went into the artists' pockets, because all the purchases were secondhand (mostly vinyl, a few CDs). I suppose the concert tickets will somewhat make up for that, but perhaps not entirely. And what music company will get money from that, other than the promoters?
Small, microcosmic anecdotes... but multiplied by millions around the world, they add up. It didn't have to be that way. When record companies started making CDs, their costs of producing and delivering a product plummeted. So what did they do? Raised the prices! Did the performers get more money? No. Did the retail outlets make more from selling them? No. It all went into record company's pockets. After they had milked off the people willing to pay more for the new technology, did they lower their prices to reflect their cost savings? No, they fought kicking-and-screaming to keep their newly-inflated profit margins.
Even today, the record companies have legal terminology in their contracts that is completely different from not only regular English, but the legal terminology as it is used in other fields, thanks to bizarre and byzantine case law built up over the years. I don't know anyone familiar with the industry --including most performers in it-- who don't get a real sense of "schedenfreude" at seeing them squirm a little today, for a slew of reasons, many of them valid. Perhaps it's... Karma?!
The only real negative in this picture is what it spells for the future of music, if the financial incentives for producing good music evaporate. One can only hope that selling ten million copies of a recording for a buck on iTunes will equate to the former selling of one million copies of an LP for ten bucks, and people will still be motivated to make good music. Perhaps if the Internet removes the record-company middleman from the equation in a way that still allows music creators to prosper, there will be continued generation of good music. (OF course, what constitutes "good" is fodder for another discussion.

) That might not be an entirely bad thing!
Then there is the issue of a tangible product versus an intangible one. Personally, I like to own a record, CD or tape that I can touch, that I can put onto or into a machine for playback... but I can understand those who ask, "Why, when an intangible download is just as quick or quicker, and sounds just as good?"
Music will always be with us; it is hard-wired into being human. Cavemen probably chanted and thumped percussion around the campfire, many millenia ago, and our descendants are unlikely to stop that process. But there is nothing that says there must always be a music industry producing discs. That didn't exist until the previous century (and a bit), and might not survive the current century. But music will be with us, and as long as some of us are alive, so will at least some of the world's supply of tangible discs!