I've noticed distinct audio differences (more subtle than skipping or failure to play) on some CDR's compared with others. In general it's the cheapo spindles full that give problems, but not always.

I assume the problem is caused by the disc being less than perfectly readable by a consumer CD mechanism, and so the error correction/over sample/other widgets are working over time. I doubt the same problem exists if you use a CD ROM drive to play the disc (or more modern CD player, perhaps).

Rob