Good point. There's recently been the discussion of the original Carpenters master tapes deteriorating over time, (now they're as deteriorated as you can get, having been barbecued in the fire - tragedy!!!!!), so master copies done at different times will be of different quality. I've just bought a set of CDs that have rare Australian singles on them. Most of these are by local artists who had one, two, three or four hits back in the 70s and then disappeared, (or some limped on into the current era). My point is that a lot of this material has never appeared on CD before. With it being mastered for CD when the original tapes were between 37 and 47 years old, you can really hear that the recordings have deteriorated. In most cases, the original scratched old singles sound better than these newly-released CD versions.