I feel that singarounds with only singers in isnt the best idea (UK) I personally prefer a mix of non singing audience with singers as this makes for folk 'entertainment' the best example I have of this is Gainsbrough folk club when I visited a year or two ago

I do not like open mike as I sing unaccompanied and prefer smallish venues

Whitby singarounds in the old Tap could take 2 hrs to get one song not surprising then that people were complaining

Wall to to wall singers isnt a good idea but does make a great wall of sound in choruses!!

Ray