Processing (vocal) recordings with the newly found Auacity program seems to be limited to an echo effect that cannot be changed: you either switch on or off. Can it be modified?
Is there any ‘reverb’ (hall) effect know i.e. as a plug-in?
Yes, it’s called Gverb.
It’s not easy to use, but the wiki does a good job of giving some starting settings:
http://audacityteam.org/wiki/index.php?title=GVerb
I recommend FreeverbToo . I believe The hall reverb you want is already the default setting! If not, just adjust the Room Size, Wet, and Dry presets. Good luck! 