Quoted from Mr_Tantrum:
Requires the free Nyquist plugins | https://wiki.audacityteam.org/wiki/Download_Nyquist_Plug-ins#download
Process is as follows once plugin is installed (you can also script it):
1) Launch Audacity and load mono file
2) Highlight entire wave image by double-clicking with your mouse, copy, then paste to create 2 identical tracks
3) Click the black down triangle on the top track and select "Make Stereo Track" to join the two mono tracks
4) Double click track to highlight, click on "Effect" menu, then click Pseud-Stereo to launch the settings window
5) Set desired settings (my are 10% delay factor & 80% Effect mix for the Right (lower) channel) then click OK button (or you can preview) to apply effect.
6) Export WAV audio as normal
Thanks for the details. I will try it. If it helps with the vocal quality, it would be worth it.