The dialog to add another entity to a group of existing relationships (e.g., "member of" where there already are members) is supposed to be prepopulated with those attributes that all existing relationships have in common. However, it actually has more; e.g. on https://beta.musicbrainz.org/artist/b86bf49a-9097-4faf-9ad5-ada6dd8fe459/edit I get "baritone vocals" and "other vocals" even though only a few of the other members have these attributes.