Can someone explain how this could happen?

I have 2 quirks I've been trying to figure out, dealing with audio cd's.
The first one, was actually a computer CDROM drive, somebody dropped it and put it back into a computer. This drive would from then on only play the vocal tracks from any audio CD. We tried many CD's that day, from Nine Inch Nails, to Stone Temple Pilots, some rap artists... and all of them played the same way. No music, only the lead vocals.
Recently, my friend's car CD player broke, and it displayed the opposite behavior. No matter what CD was played only the music/background vocals were audible, not the lead vocals.
In both cases the music was still playing in stereo, so it was not a case of simply the left or right channel being cut.

From what I've been told, there is no discrete vocal channel on the audio CD format, correct? These 2 cases seem to negate this. If the vocals were not a seperate track, how could they or the background be cut?

I have been searching for a way to duplicate this at home, for one because I'd love to extract some vocal tracks to do some remixing of songs (a hobby I enjoy), and second just because I'm curious as to how this can happen by accident, but yet noone offers any kind of hardware or software to do exactly this. Strange, since I've found it is indeed possible.
Anyone have any insight on this mystery?