The MiniDiscs I most enjoy stumbling across are the ones where I’d made an unlabelled (except for possibly noting the month/year) “mixtape” back in the day and being reminded of a point in time. It’s interesting being reminded of what I’d been listening to in, say, May 2001 or August 1998.
These were improvements in ATRAC encoding. Type R was a 2 pass system that was incorporated into portables when processing power became powerful enough to do the extra processing. Type S improved the ATRAC3 performance in a similiar fashion. Both of these changes were to the encoder and required no changes to the playback processing