Likely causes of the fall of the music.
The fall of the music industry might be due to the RIAA and their promotion of pop stars over rock bands. Probably not. A bigger problem is that most mainstream musicians don't write their own music. Why do acts such as Depeche Mode, NIN, Tom Petty, Metallica, U2, Madonna, Prince, etc stick around? They write their own music.
I don't think piracy can be the true downfall of the music industry. In almost every venue there is the 80/20 rule. 80% of downloads are done by 20% of the people. 20% of the people might affect a song or album billboard standing from 1st to 5th or 6th if they were only downloading the one album. Likely they are affecting all billboard tracks the same.
DRM is not the problem with Amazon and iTunes. It is the file quality. Beatport, NIN official torrents and some other sources provide files that are high quality. The same or better than a CD. Audiophiles’ (who are likely the 20% that buy 80% of non-compressed music) buying habits have not really changed.
Piracy and legal downloads are not without their problems.
First thing to consider is quality. Sure an MP3 might be good enough for those iPod ear-buds in the gym. These files are nowhere near good enough quality for a DJ. A Lossless file that is of high enough quality for a DJ will be a larger file that is too big for many people.
Bandwidth is a problem with piracy as with paid downloads. It can be a bigger problem for pirates because they likely are downloading more. Without the bandwidth to download the highest quality lossless files a newer better version (like DVD -> Blu-Ray) will show up.
Also storage space tends to be an issue for pirates. If you were to try to download every file available on just one piracy network or from The Pirate Bay you would quickly run out of space no matter how much hard drive space you have. This also causes problems for people who get tons of iTunes gift cards.