Breaking the audio CD standard in order to try to avoid people making direct digital copies of CDs has been there for many years. The idea is that some computer CD drives have, for some reason, a poorer quality error correction logic in them which causes them to not to be able to correct every error in the CD. However, this happens only in some drives and not all (eg. my DVD drive can read digitally many "copy-protected" audio CDs just fine in linux even though "in theory" it shouldn't be possible).
DRM is the latest hip in music business. The idea is a bit the same as with a very old attempt at disallowing copying LPs to tapes: By making the copying hardware refuse to copy what shouldn't be copied (in the case of casette recorders they were supposed to prevent copying of any sound that had a constant 1 Hz frequency in it; this didn't gain any popularity though). Computers and hand-held devices capable of playing music are much more complicated devices than casette recorders and thus the attempted means to prevent copying are also more complicated. An attempt has been made to introduce DRM to Windows and to several so-called mp3-players (such as iPod).
There's one thing I don't understand in any of this, though, and it's how naive the music publishers seem to be.
In both cases they seem to think that making an DA-AD conversion of the music destroys the music so much that it's completely not worth listening anymore and thus nobody will bother doing that, and thus preventing pure digital copying is more than enough to prevent music piracy, and for this reason they are spending huge amounts of money in order to achieve this.
In layman terms a DA-AD conversion means that you play music which is in digital format (eg. in a CD or mp3) with any device, connect the analog audio output of the device to the analog audio input of another device and then use that second device to sample this input to digital format (such as mp3).
For some reason music publishers seem to think that this process destroys the sound too much for anyone to bother. I wonder if they have ever tried doing that themselves. Even with cheap devices the result is perfectly acceptable and most people don't hear any difference. Even if a difference could be heard when playing both versions side-by-side, the difference is so minimal that it doesn't matter in practice.
The problem is that no matter how much protection a device has, it has to play the music correctly or no-one would buy it. It's that simple.
So I find all this fuss about copy protections and DRM simply hilarious because they are so trivial to circumvent and the result is completely acceptable. Just take eg. an mp3 player with any amount of protections you want, connect its audio output to the audio input of the computer, play the song you want to copy and sample it in the computer, and that's it: You have a completely protection-free version of the music. It might not be an exact bit-by-bit copy of the original, but completely acceptable. You will most probably not hear any difference.
So why all the fuss about digital copy protection? Why bother? It's not going to stop people from copying the music anyways. Why spend millions and millions of dollars to develop such protections which are so trivial to circumvent by anyone?
The music industry is naive to the extreme.