Sounds like a classic case of noise masquerading as clues. Let’s first isolate the hiss – sample it, run a spectral analysis, see if any frequencies repeat or sync with the tape’s frame rate. If there’s a pattern, we can treat it like a cipher: map the spikes to bits, look for repeats, maybe even run a quick brute‑force on simple substitution. Got the tape file or a recording of that hiss? I can crunch the numbers for you.