I accompanied myself on a large Nepalese singing-bowl by way of a drone (although I couldn't imagine myself doing that in a singaround somehow)

I think I would, except that my singing bowl is pitched at a rather sharp D and nobody else could join in. I could always tune my Black Sea fiddle to it.

I find exotic instruments go down pretty well in singarounds, except with the small self-righteous minority who think folk is defined by Dylan. The more traditionally-oriented the participants the weirder you can get.