NBTV recording on paper tape.

[Stephen]

That might work, the trace will look very similar to a optical sound trace on a movie. The problem is if you use ink and paper instead of film or photo-paper the paper has to move very fast to get a clear signal.

Yes, I suspect that recording speed would have to be relatively high, but the concept appears to be sound "on paper".

[Stephen]

Mr Baird seems to have considered recording on paper tape at an early date. See his British Patent 324,904, filed 4 October 1928, in the Patents and Articles section. The level of detail in the specification and figures indicates that he may have reduced the scheme to practice using chemically coated paper tape.