How to do audio restoration?

Here is the YT clip. https://youtu.be/6bIUXgVZz9A?si=L2Cm_Aj0oxSaAYWK

The source tapes are slow speed reel to reel recorded somewhere between 1953 and 1968. The audio remains basically the same until 57:50 where the sound suddenly changes and stays that way until the end. See attached RX display. Comments?

This is an audio forum and this is about the audio. Not interested in comments about religion.









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