Thanks for that - I guess I should rephrase my question ( I know how to map
the audio channels)
How can I generate the audio TC to map to channel 3?
I guess I can stripe a tape with relevant TC & capture timecode output back
in as audio but that seems a long-winded way of achieving it (esp as final
delivery is Quicktime).
Googling finds this for Avid & FCP:
Any such method in PPro?
If I understand your question correctly, and if I understand the tutorial correctly, you should check out Pr's Timecode Effect. Add the 3rd audio track to its own, new sequence, then nest the new sequence in the parent sequence. You'll get a "phantom" video track with the nested sequence to which you can apply the timecode effect.
That all assumes that I have a clue, which I may not.