DualDiscs! Do you remember them?
The idea was that they were double-sided discs, with one being a regular CD audio album and the other being DVD. The DVD side would usually have the full album at a higher sample rate, and often included bonus video material like making of documentaries and music videos.
These felt like a very cool idea and were a definite step up over Enhanced CD in terms of the quality of the bonus content, as even a single layer DVD was more than enough for a few standard definition music videos. Of course, they were also easier to damage and had compatibility problems with some players - though the music industry probably didn't mind that they were harder to rip.
Ultimately, DualDiscs were not on the market for very long. The ongoing decline of audio CD sales didn't help, and audiophiles ultimately preferred Super Audio CD over DVD Audio. As a result, I've only got these two - System Of A Down's Hypnotize and Fear Factory's Transgression, the latter of which doesn't seem to have had a European release.
