Simon - I love those Living Stereo SACDs and snagged up a couple of dozen titles when they were cheap and plentiful (perhaps they still are?). Beyond the exceptional fidelity I'm fascinated by the performances which I find more adventurous than many contemporary interpretations. They also predate the practice of excessively editing together different takes to create the 'perfect' performance on record. So I hear the occasional clam, rhythmic or intonation issue as well as coughing and/or sneezing on the live audience recordings. But none of that detracts from my enjoyment. Rather it adds to the natural and authentic feel of the vintage performances for me.
The original RCA Living Stereo Remastered SACDs were transferred from the original analog tapes by the team at Soundmirror - the same engineers who are doing the "Fresh" series recordings of the Pittsburgh Symphony Orchestra from Reference Recordings on Multichannel SACDs and Multichannel DSD Downloads. A talented group.
http://store.acousticsounds.com/index.cfm?get=results&searchtext=pittsburgh,symphony&categoryID=4
https://referencerecordings.nativedsd.com/