In order to better understand how member groupings work, and the use of criteria, we can look at the criteria in some specific examples. Making Music Platform comes with three default member groupings; "Regular Members", "Active Singers", and "Members and Helpers". The criteria specified for these member groupings are shown below.
These screenshots come from the page you see when you update each member grouping.
The "Regular Member" and "Members and Helpers" criteria above show that the definition of a regular member (or helper) is based solely on their membership of the club/chapter irrespective of whether they actually participate in any of the group's ensembles. And the definition of an active singer is based solely on their participation in an ensemble, regardless of their club membership. In other words, an active singer may not be a member of the club/chapter, and a regular member may not be an active singer.