I am deducing it based on the fact that if one person is threatening someone by talking to them in person with no one else around, then he said she said accusations will not be sufficient to convict one of witness tampering in a criminal trial.
Was it? It is pretty well known that one of the main obstacles for populations such as poorer people, women, minorities, or anyone else in a position position where someone has power over them that they can be coerced into questionable activities and they have no recourse because there is no proof.
This is correct if your only goal was to secure a conviction, but you are forgetting that when witness tampering is occurring, there is already a judge who is very willing to hear evidence about it. The integrity of their court is at stake. They absolutely do not require an audio recording to make any number of potent orders to protect you. The indirectness of the threat and its unsuitability to curing by judicial power is more of a problem than the lack of audio recording.
Your best bet if you care about delivering the evidence is probably to leverage the power of the judge, ventilate it and get the people threatening you to retreat. If you do that, you transform a threat behind closed doors (not to do something) into a retaliation for something real that you did (telling the court about tampering) that you can tell your tenure committee about later. In sum, open justice is designed to expose these things, it is far and away the best forum for it, so better to use it while you can.
My guess is recording laws probably grew from eavesdropping laws so perhaps in some situations you could setup an eavesdropper to serve as a collaborating witness.
Or they could've attempted to intimidate you while you were in a crowd.
Otherwise it would be on reputation alone, just like now.
