Is it or will it be possible to place a player in more than one group?
As far as I know, it’s not possible at the moment.
Would you want the player in two groups simultaneously? I can’t immediately imagine why you’d want that.
One player moves from one group to another after some time.
And maybe this is better done with layouts, but could it be good to make two groups of musicians that have a common piece in their repertoire where one musician is part of both groups?