I lost track at some point which tracks I applied noise reduction of the beast to. Won’t be in the history as I’ve worked on this project over some time. Is there any way to tell if this particular effect has been applied to a track?
It may be possible to tell from the spectrum … https://manual.audacityteam.org/man/plot_spectrum.html
The distance between the peaks & the troughs will be greater in the noise-reduced version.